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K S Bhat

Publications and source records attributed to K S Bhat.

At least 19 recordsLinked to original sources
PubMed1992

Secondary structure of the pentraxin female protein in water determined by infrared spectroscopy: effects of calcium and phosphorylcholine.

The secondary structure of hamster female protein in aqueous solutions in the presence or absence of calcium and phosphorylcholine has been investigated using Fourier transform infrared spectroscopy. Our present studies provide the first evaluation of the secondary structure of FP and its calcium- and phosphorylcholine-dependent conformational changes. Quantitative analysis indicated that FP is composed of 50% beta-sheet, 11% alpha-helix, 29% beta-turn, and 10% random structures. Calcium- and phosphorylcholine-dependent infrared spectral changes were observed in regions assigned to beta-sheet, alpha-helix, turn, and random structures. The infrared-based secondary structure compositions were used as constraints to compute theoretical locations for the different secondary structures along the amino acid sequence of the FP protein. Two putative calcium-binding sites were proposed for FP (residues 93-109 and 150-168) as well as other members of the pentraxin family on the basis of the theoretical secondary structure predictions and the similarity in sequence between the pentraxins and EF-hand calcium-binding proteins. The changes in protein conformation detected upon binding of calcium and phosphorylcholine provide a mechanism for the effects of these ligands on physiologically important properties of the protein, e.g., activation of complement and association with amyloids.

Alpha-Globulins↗
PubMed1991

Secondary structure analysis of the scrapie-associated protein PrP 27-30 in water by infrared spectroscopy.

A protease-resistant form of the protein PrP (PrP-res) accumulates in tissues of mammals infected with scrapie, Creutzfeldt-Jakob disease, and related transmissible neurodegenerative diseases. This abnormal form of PrP can aggregate into insoluble amyloid-like fibrils and plaques and has been identified as the major component of brain fractions enriched for scrapie infectivity. Using a recently developed technique in Fourier transform infrared spectroscopy which allows protein conformational analysis in aqueous media, we have studied the secondary structure of the proteinase K resistant core of PrP-res (PrP-res 27-30) as it exists in highly infectious fibril preparations. Second-derivative analysis of the infrared spectra has enabled us to quantitate the relative amounts of different secondary structures in the PrP-res aggregates. The analysis indicated that PrP-res 27-30 is predominantly composed of beta-sheet (47%), which is consistent with its amyloid-like properties. In addition, significant amounts of turn (31%) and alpha-helix (17%) were identified, indicating that amyloid-like fibrils need not be exclusively beta-sheet. The infrared-based secondary structure compositions were then used as constraints to improve the theoretical localization of the secondary structures within PrP-res 27-30.

Acetylglucosamine↗
PubMed1991

Effect of pigmentation on glutathione redox cycle antioxidant defense in whole as well as different regions of human cataractous lens.

'Reactive oxygen species', generated within the lens, are implicated in the deepening of nuclear pigmentation leading to browning of the human cataractous lens. The present study, which was carried out in senile brunescent cataracts, deals with changes in the antioxidant glutathione redox cycle defense system during the progression of browning (yellow to brown) in different regions of the human lens. A significant reduction in the levels of reduced glutathione was noted in the cortical and nuclear regions of the brown lens as compared to yellow lens, despite normal glutathione reductase activity. The rate limiting enzyme of the hexosemonophosphate shunt pathway, glucose 6-phosphate dehydrogenase, and the important oxidant scavenger enzyme, glutathione peroxidase, showed significant changes in opposite directions (glucose 6-phosphate dehydrogenase increased and glutathione peroxidase decreased), only in the cortical region of the brown lens as compared to yellow lens. The significance of the present findings in relation to the overall biochemical mechanisms underlying browning of the lens tissue in human cataracts is discussed.

Aged↗
PubMed1991

The opacity proteins of Neisseria gonorrhoeae strain MS11 are encoded by a family of 11 complete genes.

Variants of Neisseria gonorrhoeae MS11 show distinct colony morphologies because of the expression of a class of surface components called opacity (Opa, PII) proteins. Southern analyses combined with molecular cloning of genomic DNA from a single variant of MS11 has identified 11 opa genes contained in separate loci. These opa genes code for distinct opacity proteins which are distinguishable at their variable domains. The opa gene analyses were also extended to divergent variants of MS11. These studies have shown that, during in vitro and in vivo culture, 10 of the 11 opa genes did not undergo significant change in their primary sequence. However, in these variants, one gene (opaE) underwent non-reciprocal inter-opa recombinations to generate newer Opa variants. Phylogenic analysis of the opa gene sequences suggests that the opa gene family have evolved by a combination of gene duplication, gene replacement and partial inter-opa recombination events.

Amino Acid Sequence↗
PubMed1991

Prevalence of gene sequences coding for hypervariable regions of Opa (protein II) in Neisseria gonorrhoeae.

Opas (protein IIs) are a family of surface-exposed proteins of Neisseria gonorrhoeae. Each strain of N. gonorrhoeae has multiple (10-11) genes encoding for Opas. Identifiable elements in opa genes include the coding repeat within the signal sequence, conserve 5' and 3' regions, and hypervariable regions (HV1 and HV2) located within the structural gene. N. gonorrhoeae strains appear to have many biological properties in common that are either HV-region-mediated or associated with the presence of specific HV regions, suggesting that HV regions could be found in many clinical isolates. Oligonucleotides from three source strains representing three conserved regions of opa, 12 HV1 regions, and 14 HV2 regions were used by dot blot analysis to probe 120 clinical isolates of N. gonorrhoeae. The probe for the coding repeat hybridized to all 120 strains, the 3' conserved-region probe reacted with 98% of the strains, and the 5' conserved-region probe with 90% of the strains. Nine HV1 probes hybridized to 3.3-39.2% of the strains, and 13 of the HV2 probes hybridized to 1.7-25% of the isolates. Analysis of the number of probes that hybridized to each of the isolates showed that 19% did not hybridize with any of the HV1 probes and 25% did not hybridize with any of the HV2 probes. Approximately three-quarters of the isolates hybridized with one, two or three of the HV1 probes or one, two or three of the HV2 probes; 89% of the isolates hybridized to least one HV1 or one HV2 probe. The data indicate that some genes encoding HV regions of N. gonorrhoeae Opa proteins are widely distributed in nature.

Bacterial Outer Membrane Proteins↗
PubMed1989

Characterization of primary transcripts and identification of transcription initiation sites on the heavy and light strands of mouse mitochondrial DNA.

Total RNA from Ehrlich ascites mitochondria pretreated with RNase-free DNase was capped in vitro with [alpha-32P]GTP and guanylyl transferase. The cappable RNAs representing the primary transcripts show a heterogeneous size distribution with four major species of 46, 63, 94, and 152 nucleotides and four minor species of 19, 24, 104, and 790 nucleotides in size. Hybridization with the D-loop DNA probes shows that the 19-nucleotide-long capped RNA is coded by the H-strand of mitochondrial DNA while the rest are coded by the L-strand. S1 nuclease mapping and primer extension analyses suggest the occurrence of a transcription initiation of H-strand at about 19 nucleotides upstream from the start of the tRNA(Phe) gene. All of the L-strand cappable RNAs have a common 5' end mapping to nucleotide 16,183 +/- 5 of the genome. The 3' ends of four major cappable RNA species line up to the conserved sequence boxes, putative start sites of DH-DNA; and in fact about 2% of these cappable species are found to exist as DNA-linked RNA under steady-state conditions. The 3' end of the 790-nucleotide cappable RNA lies close to the start of the tRNA(Pro) gene, suggesting that it may be the true precursor of L-strand transcript endonucleolytically processed at the 3' end. The level of L-strand-coded cappable RNAs varies markedly under different growth conditions. Treatment with cycloheximide results in a reduction while chloramphenicol caused over 3-fold induction, suggesting that these "primer" RNAs may have an additional regulatory function.

Animals↗
PubMed1985

Expression of the cytochrome b-URF6-URF5 region of the mouse mitochondrial genome.

The nature of RNA coded by the only light-strand (L-strand) open-reading frame unidentified reading frame 6 (URF6) was studied by using a variety of single- and double-strand DNA subclones derived from the 3.6-kilobase (kb) cytochrome b (cyt b)-URF5 coding region of the mouse mitochondrial genome. Northern blot experiments using single-strand-specific M13 clones indicate that both the heavy (H) and L strands of this genomic region are symmetrically transcribed and processed into poly(adenylic acid) [poly(A)] RNAs of comparable size. The 1.2- and 2.4-kb RNAs coded by the H strand, putative mRNAs for cyt b and URF5 reading frames, respectively, are derived from a common precursor of 3.6-kb RNA. The L-strand-coded 1.15-kb RNA, on the other hand, is derived from a short-lived precursor of 3.6-kb RNA by a multiple-step processing involving a 2.4-kb intermediate RNA. The S1 nuclease protection experiments using both the 3'- or 5'-end-labeled DNA probes and also affinity-purified 32P-labeled RNA probes indicate that the 1.15-kb RNA maps between the start of the URF6 reading frame (3' end) and a region 590-600 nucleotides to the 5' end of this reading frame. The 1.15-kb RNA thus contains the entire URF6 coding sequence and an about 590-nucleotide-long 3' untranslated region. The molar abundance of the three mRNAs in the steady-state mitochondrial RNA varies markedly. The 1.15-kb URF6 mRNA is only one-tenth the level of 1.2-kb cyt b mRNA, although it is nearly as abundant as the 2.4-kb URF5 mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Nature of steady-state and newly synthesized mitochondrial messenger ribonucleic acids in mouse liver and Ehrlich ascites tumor cells.

The steady-state mitochondrial mRNAs in Ehrlich ascites tumor cells and mouse liver were identified by the Northern blot analysis using nick-translated mtDNA and 32P-labeled cDNA probes. The steady-state mRNA species were compared with the poly(A)-containing RNA synthesized in vitro in isolated mitoplasts. The results show that the isolated mitoplast system can efficiently transcribe almost all of the poly(A)-containing RNAs detected in the steady-state RNA population. It is also seen that the mode of transcription and maturation of mitochondrial mRNAs in different mouse tissues are identical. The results of Northern blot analyses suggest that there may be at least two different modes of mRNA maturation depending upon if the reading frames are interrupted by tRNA cistrons or not. mRNAs for reading frames with adjacent tRNA cistrons downstream appear to be processed from very short-lived precursors. In contrast, mRNAs coded by adjacently located reading frames with no interrupting tRNA genes such as URF3 -cyt ox III and URF5 -cyt b are processed from relatively long-lived precursors. The in vitro pulse-labeling studies also show that almost all of the poly(A)-containing mRNAs are transcribed at nearly identical rates, suggesting that the major regulation of mt gene expression may occur at the level of translation or mRNA decay. The present experiments have also identified a 1.85-kb poly(A)-containing RNA as the putative URF5 mRNA.

Animals↗
PubMed1983

Distribution of HMW proteins and crystallins in cataractous lenses from undernourished and well-nourished subjects.

This paper presents results of a comparative study of the HMW proteins and crystallins from 9900 g supernatant fraction of cataractous lens homogenate between undernourished and well-nourished subjects. The proportion of HMW protein from cataractous lenses obtained from undernourished subjects was markedly reduced, the proportion of alpha-crystallin was increased and the proportions of beta- and gamma-crystallins were similar as compared to well-nourished subjects. Values of insoluble/soluble protein ratios were significantly higher in the former group compared to the latter. These results suggest that the process of lens protein insolubilization occurs earlier or faster in undernourished subjects.

Cataract↗
PubMed1982

Changes in lens proteins in undernourished and well-nourished patients with cataract.

1. Patients with cataract were classified into undernourished (twenty-eight subjects) and well-nourished (twenty-seven subjects) groups based on the anthropometric index, weight (kg)/height (m)2. Those with a value for the index of less than 18 were considered as undernourished. 2. Lenses were classified into four groups on the basis of nuclear colour as proposed by Pirie (1968). Lenses of pale uniform colour or yellow colour were included in group 1, those with brownish-yellow nucleus in group 2, those with a yellowish-brown nucleus in group 3 and those with brown nucleus in group 4. 3. Irrespective of group, the wet weight, dry weight, percentage moisture and total protein content of cataractous lenses from undernourished patients were similar, as were the corresponding values for well-nourished patients. On the other hand, the percentage of soluble proteins in lenses tended to decrease with deepening of nuclear colour in both groups of patients. Further, soluble protein concentrations in lenses from undernourished patients were significantly lower as compared to those from well-nourished patients. 4. The results suggest that nutritional factors could influence the composition of cataractous lenses.

Adult↗