PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “cryptic proteins”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1998

T cell cross-reactivity to heavy metals: identical cryptic peptides may be presented from protein exposed to different metals.

The mechanisms by which metals induce activation of T cells and thus produce allergic and/ or autoimmune reactions are still obscure, and the same is true for the mechanisms that underly T cell cross-reactivity to different heavy metal ions. In the present study, we investigated induction by metals of T cell reactions to cryptic peptides of bovine RNase A. Murine CD4+ T cell hybridomas specific for cryptic RNase peptides presented from Au(III)-treated RNase were used as detection probes. We showed that in vitro treatment of RNase with Pd(II), Pd(IV), Ni(IV), and partially Pt(IV), but not Au(I), Ni(II), or Pt(II), induced presentation of the same cryptic peptides as those presented from Au(III)-treated RNase. That the former heavy metal ions, but not the latter, were able to alter the antigenicity of RNase was reflected by their ability to induce conformational changes of RNase, as detected by circular dichroism spectroscopy. Furthermore, upon immunization against RNase pretreated with these metals, CD4+ T cell hybridomas specific for unidentified cryptic peptides were obtained. In conclusion, "metal-specific" T cell reactions may be directed against cryptic peptides, and metal cross-reactivity in allergic individuals might be due to metal-induced presentation of overlapping, but not identical, panels of cryptic peptides.

Animals↗
PubMed2003

Interaction of Epstein-Barr virus latent membrane protein 1 with SCFHOS/beta-TrCP E3 ubiquitin ligase regulates extent of NF-kappaB activation.

The Epstein-Barr virus latent membrane protein 1 (LMP1) is pivotal in the transforming activity of this virus. We found that the common LMP1-95-8 variant interacts with Homologue of Slimb (HOS), a receptor for the SCFHOS/betaTrCP ubiquitin-protein isopeptide ligase (E3) via one canonical and one cryptic HOS recognition site. These sites are mutated or deleted in the tumor-derived LMP1-Cao variant, which did not bind to HOS. Mutations within these sites on LMP1-95-8 abrogated HOS binding and increased transforming activity of LMP1. HOS did not regulate stability of LMP1-95-8 unless it was mutated to bear additional lysine residues near the cryptic motif. LMP1 proteins that could not bind to HOS exhibited an increased ability to induce IkappaB degradation and NF-kappaB-mediated transcription without further increase in activation of IkappaB kinases. Expression of LMP1-95-8 reduced the levels of endogenous HOS available to interact with phosphorylated IkappaBalpha. Degradation of IkappaBalpha and dose dependence of NF-kappaB activation by LMP1-95-8 were promoted by co-expression of HOS. Our data suggest that LMP1-95-8 is a pseudo-substrate of SCFHOS/betaTrCP E3 ubiquitin ligase and that interaction between LMP1 and HOS restricts the extent of LMP1-induced NF-kappaB signaling. We discuss the potential role of this mechanism in transforming and cytostatic effects of LMP1 variants in cells and Epstein-Barr virus-associated tumors.

Amino Acid Sequence↗
PubMed1988

A novel insertion sequence in the cryptic plasmid of Neisseria gonorrhoeae may alter the B protein at the translational level.

A variant of the cryptic plasmid of Neisseria gonorrhoeae, 4.4 kb in size, was isolated and characterized at the molecular level. This variant harbored a 156-bp insertion which was located between coordinates 3134 and 3135 within the putative cppB gene using the 4.2-kb cryptic plasmid, pJD1, as a reference. The insertion contained a novel EcoRI site and several elements of symmetry (both direct and inverted repeats). Stop codons present in the insertion interrupted the coding capacity of the cppB gene. Although the insertion was within one of two previously characterized 44-bp repeats purportedly involved in site-specific recombination, it was distinct from a 54-bp segment deleted in some cryptic plasmids. The presence of the insertion suggests a mechanism of modulating the expression of the cppB gene at the translational level through DNA rearrangement.

Amino Acid Sequence↗
PubMed1996

Cryptic origin of SPAI, a plasma protein with a transglutaminase substrate domain and the WAP motif, revealed by in situ hybridization and immunohistochemistry.

SPAI, originally isolated as a sodium/potassium-ATPase inhibitor and now considered to be a proteinase inhibitor of unknown specificity based on its similarity to elafin (an elastase inhibitor), is a new type of plasma protein that has a transglutaminase substrate domain, which serves as an anchoring sequence to be covalently cross-linked at target sites. To determine the source of SPAI, we carried out in situ hybridization and immunohistochemistry using an antisense cRNA probe and an antiserum against recombinant SPAI, respectively. Since previous RNase protection analysis had indicated that SPAI mRNA is almost exclusively expressed in the porcine small intestine, we used its frozen sections for the staining. The lower crypt was decorated with both the cRNA probe and antiserum, indicating that SPAI is synthesized and secreted by the enteroendocrine cells located near the crypt base. The native form of SPAI was also characterized by Western blotting. This result together with the previous biochemical and molecular biological characterizations may set the stage for identifying the physiological roles of the conceptually very interesting protein SPAI.

Animals↗
PubMed1993

Nuclear localization signals (NLS).

Available data strongly suggest that simple karyophilic clusters of arginines and lysines in nucleus-targeted proteins signal the anchoring of these proteins to specialized transporter molecules found on the pore complex or in the cytoplasm. These peptides have been termed nuclear localization signals (NLS). Other nuclear proteins contain "split" or "bipartite" NLS hypothesized to be reconstituted by protein folding or conformational change induced by glucocorticoids. The active NLS needs to be exposed to the protein surface, the cell has invented mechanisms to expose a hidden or cryptic NLS by protein phosphorylation, dephosphorylation, dissociation of an inhibitory subunit that masks the NLS, processing of a larger precursor, and binding of a hormone to regulate the nuclear import of a protein transcription factor at a certain stage of development, or cell cycle. It is proposed (1) that a hexapeptide with four arginines and lysines (and histidines, in some cases) is a good candidate for a "core NLS," (2) that acidic domains on proteins to be imported may participate in anchoring them to the transporter cytoplasmic or pore complex NLS-receptor, and (3) that NLS have both a cytoplasmic and a nuclear function. The interaction between nuclear proteins and transporter proteins in the pore appears to be largely electrostatic and to be disrupted by the binding of mRNA molecules to the same transporter protein, functioning also for the cytoplasmic export of RNA.

Amino Acid Sequence↗
PubMed2004

Nucleus-encoded genes for plastid-targeted proteins in Helicosporidium: functional diversity of a cryptic plastid in a parasitic alga.

Plastids are the organelles of plants and algae that house photosynthesis and many other biochemical pathways. Plastids contain a small genome, but most of their proteins are encoded in the nucleus and posttranslationally targeted to the organelle. When plants and algae lose photosynthesis, they virtually always retain a highly reduced "cryptic" plastid. Cryptic plastids are known to exist in many organisms, although their metabolic functions are seldom understood. The best-studied example of a cryptic plastid is from the intracellular malaria parasite, Plasmodium, which has retained a plastid for the biosynthesis of fatty acids, isoprenoids, and heme by the use of plastid-targeted enzymes. To study a completely independent transformation of a photosynthetic plastid to a cryptic plastid in another alga-turned-parasite, we conducted an expressed sequence tag (EST) survey of Helicosporidium. This parasite has recently been recognized as a highly derived green alga. Based on phylogenetic relationships to other plastid homologues and the presence of N-terminal transit peptides, we have identified 20 putatively plastid-targeted enzymes that are involved in a wide variety of metabolic pathways. Overall, the metabolic diversity of the Helicosporidium cryptic plastid exceeds that of the Plasmodium plastid, as it includes representatives of most of the pathways known to operate in the Plasmodium plastid as well as many others. In particular, several amino acid biosynthetic pathways have been retained, including the leucine biosynthesis pathway, which was only recently recognized in plant plastids. These two parasites represent different evolutionary trajectories in plastid metabolic adaptation.

Algal Proteins↗
PubMedDate not supplied

Peptide immunization can elicit malaria protein-specific memory helper but not proliferative T cells.

We have studied the proliferative and helper T cell responses in mice to a malaria sporozoite vaccine candidate currently undergoing human trials. Following immunization of B10 (I-Ab) mice with the purified recombinant baculovirus-expressed Plasmodium falciparum circumsporozoite protein, draining lymph node cells were challenged in vitro with a series of overlapping synthetic peptides which span the construct. Surprisingly, only a single peptide from the protein was immunodominant in that it could reproducibly elicit a significant proliferative response from the immunized lymph node cells. This epitope, (NANP)n, is also the repetitive immunodominant B cell epitope of the protein. However, immunization of mice with synthetic peptides revealed at least 3 cryptic proliferative epitopes--epitopes not revealed by protein immunization--two of which represent conserved regions of the protein. While cryptic peptide-immunization did not elicit protein-specific proliferative T cells, it did reveal protein-specific helper T cells, as shown by an in vivo assay. Identification of "cryptic" epitopes not only for malaria but for other infectious diseases may aid vaccine design, especially in situations where subunit vaccines are sought.

Amino Acid Sequence↗
PubMed2006

Matrix protein of Vesicular stomatitis virus harbours a cryptic mitochondrial-targeting motif.

Vesicular stomatitis virus (VSV) is a rhabdovirus that has attracted attention of late as an oncolytic virus and as a vaccine vector. Mutations in the matrix (M) gene of VSV yield attenuated strains that may be very useful in both settings. As a result of this interest in the M protein, this study analysed various M-green fluorescent protein (GFP) fusion constructs. Remarkably, fusion of the N terminus of the M protein to GFP targeted the fluorescent protein to the surface of mitochondria. Mutational analysis indicated that a mitochondrial-targeting motif exists within aa 33-67. Expression of these fusion proteins led to loss of mitochondrial membrane permeability and to an alteration in mitochondrial organization mirroring that seen during viral infection. In addition, a portion of the M protein present in infected cells co-purified with mitochondria. This work may indicate a novel function for this multifunctional viral protein.

Amino Acid Motifs↗
PubMed2006

Selection of cryptic B-cell epitopes using informational analysis of protein sequences.

Sub-unit vaccines are synthetic or recombinant peptides representing T- or B-cell epitopes of major protein antigens from a particular pathogen. Epitope selection requires the synthesis of peptides that overlap the protein sequences and screening for the most effective ones. In this study a new method of immunogenic peptide selection based on the analysis of information structure of protein sequences is suggested. The analysis of known B-cell epitope location in the information structure of Aspergillus fumigatus proteins Asp f 2 and Asp f 3 has shown that epitopes are scattered along the sequences of proteins for the exception of sites with Increased Degree Information Coordination (IDIC). Based on these results peptides from different allergens such as Asp f 2, Der p 1, and Fel d 1 were selected and produced in a recombinant form in the context of yeast virus-like particles (VLPs). Immunization of mice with VLPs containing peptides form allergens has induced the production of IgG able to recognize full-length antigens. This result suggests that the analysis of information structure of proteins can be used for the selection of peptides possessing cryptic B-cell epitope activity.

Animals↗
PubMed1995

A protein is involved in accessibility of the inhibitor acetazolamide to the carbonic anhydrase(s) in the cyanobacterium Synechocystis PCC 6803.

A gene, zam (for resistance to acetazolamide), controlling resistance to the carbonic anhydrase inhibitor acetazolamide, is described. It has been cloned from a spontaneous mutant, AZAr-5b, isolated from the cyanobacterium Synechocystis PCC 6803, for its resistance to this drug (Bédu et al., Plant Physiol 93: 1312-1315, 1990). This mutant, besides its resistance to acetazolamide, displayed an absence of catalysed oxygen exchange activity on whole cells, suggestive of a deficiency in carbonic anhydrase activity. The gene was isolated by screening a genomic library of AZAr-5b, and selecting for the capacity to transfer the AZAr phenotype to wild-type cells. A system leading to forced homologous recombination in the host chromosome, using a platform vector, was devised in order to bypass direct selection difficulties. The putative encoded protein, 782 amino acids long, showed some homology with four eukaryotic and prokaryotic proteins involved in different cellular processes, one of them suppressing a phosphatase deficiency. The mutated allele of AZAr-5b showed an in-frame 12 nucleotide duplication, which should not interfere with translation, and might result from transposition of a mobile element. Integration into a wild-type genome of either the spontaneous mutated allele or one inactivated by insertional mutagenesis conferred the character of resistance, but not the deficiency in oxygen exchange, indicating that the two phenotypic aspects of AZAr-5b corresponded to two independent mutations. A working hypothesis explaining the phenotypes of the mutants is that the presence of the Zam protein would be necessary for the inhibitor to reach (one of) the two carbonic anhydrases present in this strain. This, however, would be a secondary action, the physiological role of the protein still being cryptic.

Acetazolamide↗
PubMed2003

Identification of cryptic nuclear localization signals in the prion protein.

Abnormal transport of C-terminally truncated prion protein (PrP) to the nucleus has been reported in cell models of familial prion disorders associated with a stop codon mutation at residues 145 or 160 of the PrP. In both cases, PrP is translocated to the nucleus in an energy-dependent fashion, implying the presence of cryptic nuclear localization signal(s) in this region of PrP. In this report, we describe the presence of two independent nuclear localization signals (NLS) in the N-terminal domain of PrP that differ in the efficiency of nuclear targeting. When acting independently, each NLS sequence mediates the transport of tagged bovine serum albumin into the nucleus of permeabilized cells. When acting together, the two NLS sequences complement each other in transporting the N-terminal fragment of PrP to the nucleus of transfected cells, where it accumulates at steady state. Interestingly, nuclear translocation of PrP is blocked completely if the N-terminal fragment is extended to include one or two N-glycans. The glycosylated PrP fragment, instead, accumulates in the endoplasmic reticulum. Extension of the N-terminal fragment to include both N-glycans and the glycosyl phosphatidylinositol anchor, as expected, directs PrP to the plasma membrane. These observations hold implications for the pathogenesis of familial prion disorders, where truncated and abnormally glycosylated mutant PrP forms may accumulate in the nucleus and initiate neurotoxicity through novel mechanisms.

Active Transport, Cell Nucleus↗
PubMed1995

Genetic organization of a small cryptic plasmid of Helicobacter pylori.

A 2.9-kb cryptic plasmid of Helicobacter pylori (Hp), pHel1, was isolated and the complete nucleotide (nt) sequence was determined. An open reading frame (ORF1) was identified encoding a putative polypeptide of 63,709 Da, the existence and correct size of which was confirmed by T7 promoter expression analysis. The ORF1 sequence showed strong amino-acid sequence identity to a recently identified putative ORF1 protein of a cryptic Hp plasmid, pHPM180, and significant homologies to putative Rep proteins of Campylobacter coli (RepB) and Pediococcus halophilus (RepA), and was therefore designated RepA. A functional role of RepA in replication of pHel1 was demonstrated by the fact that only pHel1 plasmid derivatives with an intact repA gene were able to autonomously replicate in Hp. Upstream of repA, a 22-bp sequence was recognized which was tandemly repeated four and a half times, a feature typical for many replication origins (ori) and commonly termed a DNA iteron. Analysis of the repA upstream region by primer extension identified a transcription start point for the repA mRNA, but did not correspond to known consensus promoter sequences. Southern hybridizations using pHel1 as a probe under stringent conditions revealed that homologous sequences to pHel1 were present in nearly all plasmid-carrying Hp strains, but not in a plasmid-carrying Helicobacter felis strain, suggesting that this type of replicon is predominantly found in the Hp species.

Amino Acid Sequence↗
PubMed1989

Cloning and sequencing of the gene encoding a 125-kilodalton surface-layer protein from Bacillus sphaericus 2362 and of a related cryptic gene.

Using the vector pGEM-4-blue, a 4,251-base-pair DNA fragment containing the gene for the surface (S)-layer protein of Bacillus sphaericus 2362 was cloned into Escherichia coli. Determination of the nucleotide sequence indicated an open reading frame (ORF) coding for a protein of 1,176 amino acids with a molecular size of 125 kilodaltons (kDa). A protein of this size which reacted with antibody to the 122-kDa S-layer protein of B. sphaericus was detected in cells of E. coli containing the recombinant plasmid. Analysis of the deduced amino acid sequence indicated a highly hydrophobic N-terminal region which had the characteristics of a leader peptide. The first amino acid of the N-terminal sequence of the 122-kDa S-layer protein followed the predicted cleavage site of the leader peptide in the 125-kDa protein. A sequence characteristic of promoters expressed during vegetative growth was found within a 177-base-pair region upstream from the ORF coding for the 125-kDa protein. This putative promoter may account for the expression of this gene during the vegetative growth of B. sphaericus and E. coli. The gene for the 125-kDa protein was followed by an inverted repeat characteristic of terminators. Downstream from this gene (11.2 kilobases) was an ORF coding for a putative 80-kDa protein having a high sequence similarity to the 125-kDa protein. Evidence was presented indicating that this gene is cryptic.

Amino Acid Sequence↗
PubMed1992

The N-terminal 22 amino acids encoded by the gene specifying the major secreted protein of vaccinia virus, strain Lister, can function as a signal sequence to direct the export of a foreign protein.

Cells infected with vaccinia virus strain Lister secrete a polypeptide of approximate molecular weight 35,000 (35K) into the medium. Previous studies identified a cleavable, hydrophobic region of 17 amino acids in the 35K protein which could potentially function as a signal peptide to target the protein to the secretory pathway. Here we report the use of the expression-secretion signals derived from the 35K gene to direct export and secretion of a foreign protein. Vaccinia virus recombinants carrying the bacterial chloramphenicol acetyl transferase gene (cat) immediately downstream from the promoter and the N-terminal coding sequences of the 35K gene were constructed. Our studies show that the N-terminal 22 or 42 amino acids of the 35K protein direct efficient secretion of the CAT protein. However, due to a cryptic glycosylation site within CAT, glycosylated protein was secreted, which reduced enzymatic activity. Activity was restored in the presence of tunicamycin. Removal of the glycosylation site by site-directed mutagenesis abolished glycosylation with no effect on secretion, although CAT activity was again reduced, possibly due to an effect on the active site. The results presented here demonstrate the feasibility of using the promoter and the signal sequence of the 35K gene to generate recombinant viruses for overexpression and secretion of foreign proteins.

Animals↗
PubMed1998

Glycan-regulated antigen processing of a protein in the endoplasmic reticulum can uncover cryptic cytotoxic T cell epitopes.

We and others have shown that influenza A nucleoprotein (NP) targeted to the secretory pathway cannot be processed to yield several cytotoxic T lymphocyte (CTL) epitopes in cell lines that lack the transporter associated with antigen processing (TAP). However, a large COOH-terminal fragment of NP is processed and presented in these cells. Full-length NP is cotranslationally glycosylated in the lumen of the endoplasmic reticulum at two sites distal to the major H2-Kk and H2-Db restricted CTL epitopes, and we show here that pharmacological or genetic inhibition of N-linked glycosylation, leads to the processing and presentation of both these epitopes in a TAP-independent way.

Animals↗
PubMed1985

Polypeptides encoded by cryptic plasmids from Neisseria gonorrhoeae.

Almost all clinical isolates of Neisseria gonorrhoeae harbor a small, phenotypically cryptic plasmid of approximately 4.1 kb. In this study several polypeptides encoded by two variants of such plasmids, one (pSB01C) having a deletion of approximately 50 bp as compared to the other (p31788C), have been identified, and the position of the genes for two of the proteins determined. The cryptic plasmids were cloned into the HindIII site of the vectors pBR322 and pACYC184. The resulting recombinant plasmids were transformed into the Escherichia coli minicell producing strain DS410 (minA, minB) and the plasmid-encoded proteins analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pSB01C derivatives express two distinct proteins of 22 and 16 kDa and p31788C two other proteins of 24 and 18.5 kDa. Additionally, both plasmids express common proteins of 32.5, 9, and 7.5 kDa. The genes coding for the 24- and the 7.5 kDa proteins have been mapped by restriction enzyme analysis of Tn5 insertions suppressing the expression. The additional 50 bp in p31788C are localized to the coding region of the 24-kDa protein, and the 22-kDa protein of pSB01C is possibly a shortened form of the former due to the lacking 50 bp.

DNA Restriction Enzymes↗
PubMed2002

Human exonuclease I is required for 5' and 3' mismatch repair.

We have partially purified a human activity that restores mismatch-dependent, bi-directional excision to a human nuclear extract fraction depleted for one or more mismatch repair excision activities. Human EXOI co-purifies with the excision activity, and the purified activity can be replaced by near homogeneous recombinant hEXOI. Despite the reported 5' to 3' hydrolytic polarity of this activity, hEXOI participates in mismatch-provoked excision directed by a strand break located either 5' or 3' to the mispair. When the strand break that directs repair is located 3' to the mispair, hEXOI- and mismatch-dependent gap formation in excision-depleted extracts requires both hMutSalpha and hMutLalpha. However, excision directed by a 5' strand break requires hMutSalpha but can occur in absence of hMutLalpha. In systems comprised of pure components, the 5' to 3' hydrolytic activity of hEXOI is activated by hMutSalpha in a mismatch-dependent manner. These observations indicate a hydrolytic function for hEXOI in 5'-heteroduplex correction. The involvement of hEXOI in 3'-heteroduplex repair suggests that it has a regulatory/structural role in assembly of the 3'-excision complex or that the protein possesses a cryptic 3' to 5' hydrolytic activity.

Base Pair Mismatch↗