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A S Reddy

Publications and source records attributed to A S Reddy.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of the myosins encoded in the recently completed Arabidopsis thaliana genome sequence.

BACKGROUND: Three types of molecular motors play an important role in the organization, dynamics and transport processes associated with the cytoskeleton. The myosin family of molecular motors move cargo on actin filaments, whereas kinesin and dynein motors move cargo along microtubules. These motors have been highly characterized in non-plant systems and information is becoming available about plant motors. The actin cytoskeleton in plants has been shown to be involved in processes such as transportation, signaling, cell division, cytoplasmic streaming and morphogenesis. The role of myosin in these processes has been established in a few cases but many questions remain to be answered about the number, types and roles of myosins in plants. RESULTS: Using the motor domain of an Arabidopsis myosin we identified 17 myosin sequences in the Arabidopsis genome. Phylogenetic analysis of the Arabidopsis myosins with non-plant and plant myosins revealed that all the Arabidopsis myosins and other plant myosins fall into two groups - class VIII and class XI. These groups contain exclusively plant or algal myosins with no animal or fungal myosins. Exon/intron data suggest that the myosins are highly conserved and that some may be a result of gene duplication. CONCLUSIONS: Plant myosins are unlike myosins from any other organisms except algae. As a percentage of the total gene number, the number of myosins is small overall in Arabidopsis compared with the other sequenced eukaryotic genomes. There are, however, a large number of class XI myosins. The function of each myosin has yet to be determined.

Arabidopsis↗
PubMed2001

Kinesins in the Arabidopsis genome: a comparative analysis among eukaryotes.

BACKGROUND: Kinesins constitute a superfamily of microtubule motor proteins that are found in eukaryotic organisms. Members of the kinesin superfamily perform many diverse cellular functions such as transport of vesicles and organelles, spindle formation and elongation, chromosome segregation, microtubule dynamics and morphogenesis. Only a few kinesins have been characterized in plants including Arabidopsis thaliana. Because of the diverse cellular functions in which kinesins are involved, the number, types and characteristics of kinesins present in the Arabidopsis genome would provide valuable information for many researchers. RESULTS: Here we have analyzed the recently completed Arabidopsis genome sequence and identified sixty-one kinesin genes in the Arabidopsis genome. Among the five completed eukaryotic genomes the Arabidopsis genome has the highest percentage of kinesin genes. Further analyses of the kinesin gene products have resulted in identification of several interesting domains in Arabidopsis kinesins that provide clues in understanding their functions. A phylogenetic analysis of all Arabidopsis kinesin motor domain sequences with 113 motor domain sequences from other organisms has revealed that Arabidopsis has seven of the nine recognized subfamilies of kinesins whereas some kinesins do not fall into any known family. CONCLUSION: There are groups of Arabidopsis kinesins that are not present in yeast, Caenorhabditis elegans and Drosophila melanogaster that may, therefore, represent new subfamilies specific to plants. The domains present in different kinesins may provide clues about their functions in cellular processes. The comparative analysis presented here provides a framework for future functional studies with Arabidopsis kinesins.

Journal Article↗
PubMed2001

Molecular motors and their functions in plants.

Molecular motors that hydrolyze ATP and use the derived energy to generate force are involved in a variety of diverse cellular functions. Genetic, biochemical, and cellular localization data have implicated motors in a variety of functions such as vesicle and organelle transport, cytoskeleton dynamics, morphogenesis, polarized growth, cell movements, spindle formation, chromosome movement, nuclear fusion, and signal transduction. In non-plant systems three families of molecular motors (kinesins, dyneins, and myosins) have been well characterized. These motors use microtubules (in the case of kinesines and dyneins) or actin filaments (in the case of myosins) as tracks to transport cargo materials intracellularly. During the last decade tremendous progress has been made in understanding the structure and function of various motors in animals. These studies are yielding interesting insights into the functions of molecular motors and the origin of different families of motors. Furthermore, the paradigm that motors bind cargo and move along cytoskeletal tracks does not explain the functions of some of the motors. Relatively little is known about the molecular motors and their roles in plants. In recent years, by using biochemical, cell biological, molecular, and genetic approaches a few molecular motors have been isolated and characterized from plants. These studies indicate that some of the motors in plants have novel features and regulatory mechanisms. The role of molecular motors in plant cell division, cell expansion, cytoplasmic streaming, cell-to-cell communication, membrane trafficking, and morphogenesis is beginning to be understood. Analyses of the Arabidopsis genome sequence database (51% of genome) with conserved motor domains of kinesin and myosin families indicates the presence of a large number (about 40) of molecular motors and the functions of many of these motors remain to be discovered. It is likely that many more motors with novel regulatory mechanisms that perform plant-specific functions are yet to be discovered. Although the identification of motors in plants, especially in Arabidopsis, is progressing at a rapid pace because of the ongoing plant genome sequencing projects, only a few plant motors have been characterized in any detail. Elucidation of function and regulation of this multitude of motors in a given species is going to be a challenging and exciting area of research in plant cell biology. Structural features of some plant motors suggest calcium, through calmodulin, is likely to play a key role in regulating the function of both microtubule- and actin-based motors in plants.

Actins↗
PubMed2000

A calmodulin binding protein from Arabidopsis is induced by ethylene and contains a DNA-binding motif.

Calmodulin (CaM), a key calcium sensor in all eukaryotes, regulates diverse cellular processes by interacting with other proteins. To isolate CaM binding proteins involved in ethylene signal transduction, we screened an expression library prepared from ethylene-treated Arabidopsis seedlings with 35S-labeled CaM. A cDNA clone, EICBP (Ethylene-Induced CaM Binding Protein), encoding a protein that interacts with activated CaM was isolated in this screening. The CaM binding domain in EICBP was mapped to the C-terminus of the protein. These results indicate that calcium, through CaM, could regulate the activity of EICBP. The EICBP is expressed in different tissues and its expression in seedlings is induced by ethylene. The EICBP contains, in addition to a CaM binding domain, several features that are typical of transcription factors. These include a DNA-binding domain at the N terminus, an acidic region at the C terminus, and nuclear localization signals. In database searches a partial cDNA (CG-1) encoding a DNA-binding motif from parsley and an ethylene up-regulated partial cDNA from tomato (ER66) showed significant similarity to EICBP. In addition, five hypothetical proteins in the Arabidopsis genome also showed a very high sequence similarity with EICBP, indicating that there are several EICBP-related proteins in Arabidopsis. The structural features of EICBP are conserved in all EICBP-related proteins in Arabidopsis, suggesting that they may constitute a new family of DNA binding proteins and are likely to be involved in modulating gene expression in the presence of ethylene.

Amino Acid Motifs↗
PubMed2000

A pollen-specific novel calmodulin-binding protein with tetratricopeptide repeats.

Calcium is essential for pollen germination and pollen tube growth. A large body of information has established a link between elevation of cytosolic Ca(2+) at the pollen tube tip and its growth. Since the action of Ca(2+) is primarily mediated by Ca(2+)-binding proteins such as calmodulin (CaM), identification of CaM-binding proteins in pollen should provide insights into the mechanisms by which Ca(2+) regulates pollen germination and tube growth. In this study, a CaM-binding protein from maize pollen (maize pollen calmodulin-binding protein, MPCBP) was isolated in a protein-protein interaction-based screening using (35)S-labeled CaM as a probe. MPCBP has a molecular mass of about 72 kDa and contains three tetratricopeptide repeats (TPR) suggesting that it is a member of the TPR family of proteins. MPCBP protein shares a high sequence identity with two hypothetical TPR-containing proteins from Arabidopsis. Using gel overlay assays and CaM-Sepharose binding, we show that the bacterially expressed MPCBP binds to bovine CaM and three CaM isoforms from Arabidopsis in a Ca(2+)-dependent manner. To map the CaM-binding domain several truncated versions of the MPCBP were expressed in bacteria and tested for their ability to bind CaM. Based on these studies, the CaM-binding domain was mapped to an 18-amino acid stretch between the first and second TPR regions. Gel and fluorescence shift assays performed with CaM and a CaM-binding synthetic peptide further confirmed MPCBP binding to CaM. Western, Northern, and reverse transcriptase-polymerase chain reaction analysis have shown that MPCBP expression is specific to pollen. MPCBP was detected in both soluble and microsomal proteins. Immunoblots showed the presence of MPCBP in mature and germinating pollen. Pollen-specific expression of MPCBP, its CaM-binding properties, and the presence of TPR motifs suggest a role for this protein in Ca(2+)-regulated events during pollen germination and growth.

Amino Acid Sequence↗
PubMed2000

Interaction of a kinesin-like calmodulin-binding protein with a protein kinase.

Kinesin-like calmodulin-binding protein (KCBP) is a novel member of the kinesin superfamily that is involved in cell division and trichome morphogenesis. KCBP is unique among all known kinesins in having a myosin tail homology-4 region in the N-terminal tail and a calmodulin-binding region following the motor domain. Calcium, through calmodulin, has been shown to negatively regulate the interaction of KCBP with microtubules. Here we have used the yeast two-hybrid system to identify the proteins that interact with the tail region of KCBP. A protein kinase (KCBP-interacting protein kinase (KIPK)) was found to interact specifically with the tail region of KCBP. KIPK is related to a group of protein kinases specific to plants that has an additional sequence between subdomains VII and VIII of the conserved C-terminal catalytic domain and an extensive N-terminal region. The catalytic domain alone of KIPK interacted weakly with the N-terminal KCBP protein but strongly with full-length KCBP, whereas the noncatalytic region did not interact with either protein. The interaction of KCBP with KIPK was confirmed using coprecipitation assays. Using bacterially expressed full-length and truncated proteins, we have shown that the catalytic domain is capable of phosphorylating itself. The association of KIPK with KCBP suggests regulation of KCBP or KCBP-associated proteins by phosphorylation and/or that KCBP is involved in targeting KIPK to its proper cellular location.

Amino Acid Sequence↗
PubMed2000

Bundling of microtubules by motor and tail domains of a kinesin-like calmodulin-binding protein from Arabidopsis: regulation by Ca(2+)/Calmodulin.

Kinesin-like calmodulin-binding protein (KCBP), a novel kinesin-like protein from plants, is unique among kinesins and kinesin-like proteins in having a calmodulin-binding domain adjacent to its motor domain. KCBP localizes to mitotic microtubule (MT) arrays including the preprophase band, the spindle apparatus, and the phragmoplast, suggesting a role for KCBP in establishing these MT arrays by bundling MTs. To determine if KCBP bundles MTs, we expressed C-terminal motor and N-terminal tail domains of KCBP, and used the purified proteins in MT bundling assays. The 1.5 C protein with the motor and calmodulin-binding domains induced MT bundling. The 1.5 C-induced bundles were dissociated in the presence of Ca(2+)/calmodulin. Similar results were obtained with a 1.4 C protein, which lacks much of the coiled-coil region present in 1.5 C protein and does not form dimers. The N-terminal tail of KCBP, which contains an ATP-independent MT binding site, is also capable of bundling MTs. These results, together with the KCBP localization data, suggest the involvement of KCBP in establishing mitotic MT arrays during different stages of cell division and that Ca(2+)/calmodulin regulates the formation of these MT arrays.

Arabidopsis↗
PubMed2000

The nucleotide sequence of Indian peanut clump virus RNA 2: sequence comparisons among pecluviruses.

The RNA-2 molecule of an isolate of the L serotype of Indian peanut clump virus (IPCV) was shown to consist of 4,290 nucleotides with five open reading frames (ORF). The arrangement of the ORFs resembled that in RNA-2 of Peanut clump virus (PCV) from West Africa. The proteins encoded by the ORFs in IPCV-L RNA are between 32% and 93% identical to those encoded by PCV RNA. Partial sequence data for the RNA-2 of isolates of the H and T serotypes of IPCV show that the coat and P40 proteins encoded by the 5'-most ORFs of RNA-2 of IPCV-L, IPCV-H and IPCV-T are as similar to each other as any is to the corresponding proteins of PCV. A conserved motif 'F-E-x6-W' is present near the C-termini of the coat proteins of all three IPCV serotypes and of PCV, as it is in the coat proteins of other viruses that have rod-shaped particles, such as Tobacco mosaic virus and Tobacco rattle virus. The results support the distinction of IPCV and PCV as separate virus species, but also raise the question of how the serotypes of IPCV should be classified.

Amino Acid Sequence↗
PubMed2000

Arthroscopy of the elbow: a long-term clinical review.

PURPOSE: The purpose of this study was to review a large group of patients who had arthroscopy of the elbow to determine the efficacy and relative risks of this procedure. TYPE OF STUDY: We retrospectively reviewed a convenient sample of 172 patients who underwent 187 arthroscopies of the elbow over a 7-year period. MATERIALS AND METHODS: All patients had their charts and radiographs reviewed, and 104 of these patients were also contacted for a telephone interview at an average follow-up of 42.3 months (range, 7 to 115 months). RESULTS: The procedures were performed primarily by 7 different surgeons, using all 3 standard operating positions and a variety of arthroscopic portals. The most common diagnosis was posterior impingement in 96 patients (51%), followed by loose bodies in 72 patients (31%), and degenerative joint disease in 32 patients (22%). The average preoperative modified Figgie score was 27.7 points (range, 17-43) for all patients. The average postoperative score was 45.4 points (range, 29-50), with the largest increase occurring in the pain score. There were 51 patients (56%) with an excellent surgical result, 37 patients (36%) with a good result, 12 patients (11%) with a fair result, and 4 patients (4%) with a poor result. The average modified Figgie score increased from 31.2 points (range, 22-43) to 46.9 (range, 29-50) postoperatively in professional athletes; from 26.3 to 42.6 in patients who had Workers' Compensation claims but were not professional athletes; from 29.4 to 45.6 in patients with a diagnosis of loose bodies; and from 30.1 to 43.7 in patients with degenerative joint disease. There were 3 known surgical complications (1.6%) overall, 1 of which was a patient who had a transection of the ulnar nerve requiring microsurgical repair. Of the 104 patients who were contacted, 6 patients felt that their symptoms had not improved after surgery. Eight of the 55 baseball players contacted were not able to return to their same level of competition. CONCLUSIONS: Arthroscopy of the elbow appears to be a safe and efficacious procedure with a relatively low complication rate.

Adolescent↗
PubMed2000

A novel calcium/calmodulin-regulated kinesin-like protein is highly conserved between monocots and dicots.

Recently, a novel kinesin-like protein (KCBP) that is regulated by Ca2+/calmodulin was isolated from dicot plants. A homolog of KCBP has not been reported in monocots. To determine if this motor protein is present in phylogenetically divergent flowering plants, Arabidopsis KCBP cDNA was used as a probe to screen a genomic library of maize, an evolutionarily divergent species. This screening resulted in isolation of a KCBP homolog. Comparison of the predicted amino acid sequence of the KCBP from maize (ZmKCBP), a monocot, with the previously reported KCBP sequences from dicot species showed that the amino acid sequence, domain organization, and gene structure are highly conserved between monocots and dicots. The C-terminal region of ZmKCBP, containing the motor domain and the calmodulin-binding domain, and the N-terminal tail, with a myosin tail homology region (MyTH4) and talin-like region, showed strong sequence similarity to the KCBP homolog from dicots. However, the coiled-coil region is less conserved between monocots and dicots. The ZmKCBP gene contained 22 exons and 21 introns. The location of 19 of the 21 introns of ZmKCBP is also conserved. The ZmKCBP protein is encoded by a single gene and expressed in all tissues. Affinity-purified antibody to the calmodulin-binding domain of Arabidopsis KCBP detected a protein in both the soluble and the microsomal fractions. The C-terminal region of ZmKCBP, containing the motor and calmodulin-binding domains, bound calmodulin in the presence of calcium and failed to bind in the presence of EGTA. The ZmKCBP, along with other KCBPs from dicots, was grouped into a distinct group in the C-terminal subfamily of kinesin-like proteins. These data suggest that the KCBP is ubiquitous and highly conserved in all flowering plants and the origin of KCBP predated the divergence of monocots and dicots.

Amino Acid Sequence↗
PubMed2000

Inhibition of fungal and bacterial plant pathogens by synthetic peptides: in vitro growth inhibition, interaction between peptides and inhibition of disease progression.

Four synthetic cationic peptides, pep6, pep7, pep11 and pep20, were tested alone and in combinations for their antimicrobial activities against economically important plant pathogenic fungi (Phytophthora infestans and Alternaria solani) and bacteria (Erwinia carotovora subsp. carotovora and E. carotovora subsp. atroseptica). In in vitro studies, P. infestans and A. solani were inhibited by all four peptides, while E. carotovora subsp. carotovora and E. carotovora subsp. atroseptica were inhibited only by pep11 and pep20. All peptides completely inhibited P. infestans and A. solani on potato leaves and P. infestans on tubers at concentrations comparable to the in vitro IC50 (effective concentration for 50% growth inhibition) values, suggesting that these peptides are more potent in preventing infection than in inhibiting hyphal growth in vitro. Microscopic observations of P. infestans and A. solani when treated with these peptides revealed hyphal anomalies. In tuber-infectivity assays, pep11 and pep20 reduced bacterial softrot symptoms by 50% at 2.0 to 2.30 microM and by 100% at 20 microM. In assays involving two-way combinations of these peptides, growth inhibitions of fungi and bacteria by the combinations were no more than the sum of growth inhibitions by each peptide when used alone, indicating that they act additively. pep11 and pep20 are not phytotoxic to potato plants at 200 microM. With strong and broad-spectrum antimicrobial activities of pep11 and pep20 against fungi and bacteria, and with no antagonistic activities, the expression of these peptides in transgenic potato plants could lead to enhanced disease resistance against these pathogens.

Amino Acid Sequence↗
PubMed2000

The kinesin-like calmodulin binding protein is differentially involved in cell division.

The kinesin-like calmodulin (CaM) binding protein (KCBP), a minus end-directed microtubule motor protein unique to plants, has been implicated in cell division. KCBP is negatively regulated by Ca(2)+ and CaM, and antibodies raised against the CaM binding region inhibit CaM binding to KCBP in vitro; therefore, these antibodies can be used to activate KCBP constitutively. Injection of these antibodies into Tradescantia virginiana stamen hair cells during late prophase induces breakdown of the nuclear envelope within 2 to 10 min and leads the cell into prometaphase. However, mitosis is arrested, and the cell does not progress into anaphase. Injection of antibodies later during cell division has no effect on anaphase transition but causes aberrant phragmoplast formation and delays the completion of cytokinesis by approximately 15 min. These effects are achieved without any apparent degradation of the microtubule cytoskeleton. We propose that during nuclear envelope breakdown and anaphase, activated KCBP promotes the formation of a converging bipolar spindle by sliding and bundling microtubules. During metaphase and telophase, we suggest that its activity is downregulated.

Arabidopsis Proteins↗
PubMed1999

An SC35-like protein and a novel serine/arginine-rich protein interact with Arabidopsis U1-70K protein.

The U1 small nuclear ribonucleoprotein 70-kDa protein, a U1 small nuclear ribonucleoprotein-specific protein, has been shown to have multiple roles in nuclear precursor mRNA processing in animals. By using the C-terminal arginine-rich region of Arabidopsis U1-70K protein in the yeast two-hybrid system, we have identified an SC35-like (SR33) and a novel plant serine/arginine-rich (SR) protein (SR45) that interact with the plant U1-70K. The SR33 and SR45 proteins share several features with SR proteins including modular domains typical of splicing factors in the SR family of proteins. However, both plant SR proteins are rich in proline, and SR45, unlike most animal SR proteins, has two distinct arginine/serine-rich domains separated by an RNA recognition motif. By using coprecipitation assays we confirmed the interaction of plant U1-70K with SR33 and SR45 proteins. Furthermore, in vivo and in vitro protein-protein interaction experiments have shown that SR33 protein interacts with itself and with SR45 protein but not with two other members (SRZ21 and SRZ22) of the SR family that are known to interact with the Arabidopsis full-length U-70K only. A Clk/Sty protein kinase (AFC-2) from Arabidopsis phosphorylated four SR proteins (SR33, SR45, SRZ21, and SRZ22). Coprecipitation studies have confirmed the interaction of SR proteins with AFC2 kinase, and the interaction between AFC2 and SR33 is modulated by the phosphorylation status of these proteins. These and our previous results suggest that the plant U1-70K interacts with at least four distinct members of the SR family including SR45 with its two arginine/serine-rich domains, and the interaction between the SR proteins and AFC2 is modulated by phosphorylation. The interaction of plant U1-70K with a novel set of proteins suggests the early stages of spliceosome assembly, and intron recognition in plants is likely to be different from animals.

Amino Acid Sequence↗
PubMed1999

Interaction of a kinesin-like protein with calmodulin isoforms from Arabidopsis.

In Arabidopsis and other plants there are multiple calmodulin isoforms. However, the role of these isoforms in regulating the activity of target proteins is obscure. Here, we analyzed the interaction between a kinesin-like calmodulin-binding motor protein (Reddy, A. S. N., Safadi, F., Narasimhulu, S. B., Golovkin, M., and Hu, X. (1996) J. Biol. Chem. 271, 7052-7060) and three calmodulin isoforms (calmodulin-2, -4, and -6) from Arabidopsis using different approaches. Gel mobility and fluorescence shift assays revealed that the motor binds to all calmodulin isoforms in a calcium-dependent manner. Furthermore, all calmodulin isoforms were able to activate bovine calcium/calmodulin-dependent phosphodiesterase. However, the concentration of calmodulin-2 required for half-maximal activation of phosphodiesterase is 2- and 6-fold lower compared with calmodulin-4 and -6, respectively. The dissociation constants of the motor to calmodulin-2, -4, and -6 are 12.8, 27.0, and 27.8 nM, respectively, indicating that calmodulin-2 has 2-fold higher affinity for the motor than calmodulin-4 and -6. Similar results were obtained using another assay that involves the binding of (35)S-labeled calmodulin isoforms to the motor. The binding saturation curves of the motor with calmodulin isoforms have confirmed that calmodulin-2 has 2-fold higher affinity to the motor. However, the affinity of calmodulin-4 and -6 isoforms for the motor was about the same. Based on these studies, we conclude that all calmodulin isoforms bind to the motor protein but with different affinities.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Novel antidiabetic and hypolipidemic agents. 5. Hydroxyl versus benzyloxy containing chroman derivatives.

Several thiazolidinediones having chroman moieties were synthesized and evaluated for their euglycemic and hypolipidemic activities. Some of the analogues having an aminoalkyl group as a linker between the chroman ring and 4-[5-(2,4-dioxo-1, 3-thiazolidinyl)methyl]phenoxy moiety seem to be better than troglitazone. In vitro transactivation assays of PPARgamma have been carried out with these glitazones to understand their molecular mechanism. For the first time we have found that some of the unsaturated thiazolidinediones are superior to their saturated counterpart in the in vivo assay. A more potent thiazolidinedione analogue than troglitazone is reported. Pharmacokinetic studies have shown that protection of the OH group in the chroman moiety leads to a decrease in metabolism, thereby resulting in a superior pharmacological profile.

Animals↗
PubMed1999

Novel euglycemic and hypolipidemic agents. 4. Pyridyl- and quinolinyl-containing thiazolidinediones.

A series of substituted pyridyl- and quinolinyl-containing 2, 4-thiazolidinediones having interesting cyclic amine as a linker have been synthesized. Both unsaturated thiazolidinediones 5 and saturated thiazolidinediones 6 and their various salts were evaluated in db/db mice for euglycemic and hypolipidemic effects and compared with BRL compound 11 and BRL-49653, respectively. Some of the potent compounds were converted to various salts in order to obtain improved activities. Among all the salts evaluated, the maleate salt of unsaturated TZD 5a was found to be a very potent euglycemic and hypolipidemic compound. Some of the more interesting compounds have also been evaluated in ob/ob mice and compared with rosiglitazone (maleate salt of BRL-49653). Oral glucose tolerance tests were performed in both db/db and ob/ob mice. Pharmacokinetic studies of 5a maleate are also reported. Receptor binding studies of PPARgamma by 5a/5a maleate did not show any significant transactivation of PPARalpha or PPARgamma.

Animals↗