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PubMed1989

Nucleotide sequence and genetic organization of Hungarian grapevine chrome mosaic nepovirus RNA2.

The complete nucleotide sequence of hungarian grapevine chrome mosaic nepovirus (GCMV) RNA2 has been determined. The RNA sequence is 4441 nucleotides in length, excluding the poly(A) tail. A polyprotein of 1324 amino acids with a calculated molecular weight of 146 kDa is encoded in a single long open reading frame extending from nucleotides 218 to 4190. This polyprotein is homologous with the protein encoded by the S strain of tomato black ring virus (TBRV) RNA2, the only other nepovirus sequenced so far. Direct sequencing of the viral coat protein and in vitro translation of transcripts derived from cDNA sequences demonstrate that, as for comoviruses, the coat protein is located at the carboxy terminus of the polyprotein. A model for the expression of GCMV RNA2 is presented.

Amino Acid Sequence↗
PubMed2026

Discovery of the order 'Quisvirales' redefines the evolution of RNA replication and transcription in the phylum Pisuviricota.

Genome replication in positive-stranded RNA (ssRNA+) viruses is mediated by cognate enzymes, including ubiquitous RNA-dependent RNA polymerase (RdRp). In ssRNA+ viruses with multiple open reading frames (ORFs) in their genomes, replication often is accompanied by synthesis of subgenomic RNAs (transcription) for expression of 3'-proximal ORFs. In addition, all ssRNA+ viruses with genomes larger than ~7 kb encode helicases, linking helicases to RNA genome expansion. Helicases are essential ATPases that unwind nucleic acids and are classified into six recognized superfamilies (SF1-SF6). In the phylum Pisuviricota that includes important pathogens, helicases of SF1-SF3 are integrated into multi-enzyme replicase polyprotein(s) including 3C(-like) protease (3CLpro) and RdRp. Here, large-scale mining of invertebrate metatranscriptomes and targeted genome sequence assembly uncovered six spider-associated ssRNA+ viruses that, based on their conserved 3CLpro-RdRp module in replicase polyproteins, genome size (20-22 kb), and phylogeny, form a family-like cluster in a putative order, named 'Quisvirales'. Quisviruses have similar genome and replicase architectures to enveloped coronaviruses and other nidoviruses. Notably, quisviruses encode ORFs 1a and 1b with predicted -1 programmed ribosomal frameshifting elements in the ORF1a/b overlap region. Using an original mapping approach for detecting chimeric sequencing reads, we obtained evidence that 3'-proximal ORFs are expressed via 5'-coterminal, leader-containing subgenomic RNAs. This suggests that the quisvirus subgenomic RNAs are generated through discontinuous transcription-a mechanism otherwise exclusively found in nidoviruses among the many ssRNA+ virus orders that synthesize subgenomic RNAs. Striking differences between nido- and quisviruses are, however, the RdRp being the only common core ORF1b-encoded enzyme and the replacement of the nidovirus SF1 helicase by a novel superfamily helicase. This quisvirus SF7 helicase, like the Picornavirales SF3 helicase, comprises an AAA+ (ATPase-like) domain typical for ring-forming helicases and thus must play an essential role in replication. The discovery of the order 'Quisvirales' demonstrates that viruses employing large replicase polyproteins of nidovirus-like complexity and discontinuous transcription may have evolved repeatedly from an 3CLpro-RdRp-encoding ancestor.

AAA+/RecA-like ATPase↗
PubMed1983

Bovine lymphosarcoma: expression of BLV-related proteins in cultured cells.

Bovine leukaemia virus (BLV) is known to be the aetiological agent of enzootic bovine lymphosarcoma. As the mechanism of tumour induction is unknown, we analysed the viral proteins expressed in cultured bovine cells of different origin, i.e. from enzootic or sporadic tumourous tissues, normal cells infected or not with BLV, and the reference FLK-BLV cells. We also investigated BLVs of different origins. As well as the previously described BLV polyproteins in FLK-BLV cells (pr70 and pr45) we have also found two additional polyproteins, p52 and p27. In these four proteins we observed the combined antigenicities of p24, p15 and p12. We observed an additional polyprotein in p42, with the antigenicities of the p24 and the p15 in cells derived from tumour tissue or infected in vitro with naturally occurring BLV isolates. None of these BLV-coded proteins, nor others with cross-reacting antigenicities, were encountered in non-BLV-producing cultured cells from enzootic or sporadic tumours. The use of autologous sera did not permit the detection of any proteins in addition to the above gag-coded and env-coded proteins. Thus, there is no evidence for the existence of a gag-x fusion protein which could play a role in BLV-induced tumourigenicity.

Animals↗
PubMed1987

Nucleotide sequence of the genome region encoding the 26S mRNA of eastern equine encephalomyelitis virus and the deduced amino acid sequence of the viral structural proteins.

The 26S mRNA and most of the nsP4 encoding regions of the eastern equine encephalomyelitis (EEE) viral genome have been cloned. Excluding the poly(A) tail, the 26S mRNA region was determined to be 4139 nucleotides long and to share the same general organization as that of other alphaviruses. A highly conserved region of 19 nucleotides, the putative transcriptase recognition site for 26S mRNA synthesis, was present at the 26S/42S junction region of the 42S genomic RNA. Translation of the 26S mRNA began at the first AUG (positions 59 to 61) initiation codon and continued with an open reading frame that coded for a polyprotein of 1258 amino acids ending at a UAA ochre termination codon (positions 3776 to 3778). All four putative posttranslational cleavage sites used to generate the capsid, E3, E2, 6K and E1 proteins were conserved. Transmembrane domains present in the EEE virus structural polyprotein have been identified and their functions discussed. Pairwise comparison of the deduced amino acid sequences of the polyproteins of five alphaviruses (EEE, Venezuelan equine encephalitis, Sindbis, Semliki Forest and Ross River viruses) revealed EEE virus to be more closely related to VEE virus than to the other three viruses.

Alphavirus↗
PubMed1989

The complete nucleotide sequence of swine vesicular disease virus.

The complete nucleotide sequence of the genome of the enterovirus swine vesicular disease virus (SVDV; H/3 '76) isolated from a healthy pig has been determined using molecular cloning and DNA sequencing techniques. The RNA genome was 7400 nucleotides long, excluding the poly(A) tract, and appeared to encode a single polyprotein of 2185 amino acids. The predicted amino acid sequence of the polyprotein showed close homology (around 90%) to that of the previously sequenced coxsackieviruses B1, B3 and B4, and also showed homology (around 60%) to that of poliovirus. This homology allows us to predict the possible cleavage sites of the polyprotein and to identify other features of structural and functional significance, which seem to be important to the biological integrity of the virus. A detailed analysis of homology between SVDV and coxsackieviruses shows that non-structural proteins are highly conserved whereas the structural proteins are less well conserved. The 5' and 3' non-coding regions are also conserved, although there are several divergent nucleotide stretches. These stretches may differentiate SVDV from coxsackieviruses.

Amino Acid Sequence↗
PubMed1990

Nucleotide sequence analysis of genome segment A of infectious bursal disease virus.

The nucleotide sequence of genome segment A cDNA of the STC strain of infectious bursal disease virus (IBDV) was determined and compared with sequences of the homologous genome segment of the 002-73 strain of IBDV and the Jasper strain of infectious pancreatic necrosis virus (IPNV). The STC-IBDV genome segment A was determined to be 3262 base pairs (bp), which is close to the estimated total length of 3300 bp for genome segment A in IBDV, although there is no proof that it is the real length of this genome segment. The STC-IBDV genome segment A contains two major overlapping open reading frames (ORFs). The large ORF of 3036 bp predicts a polyprotein of Mr 109,358, whereas the small ORF is 435 bp and predicts a protein of Mr 16,550 in STC-IBDV. STC-IBDV and 002-73-IBDV polyproteins are closely related (97.4% amino acid homology). Most of the amino acid mismatches are in VP2 sequences, mainly within the area of the conformation-dependent epitope. Comparison with the Jasper-IPNV polyprotein reveals levels of amino acid sequence homology of about 40% in VP2, 32% in VP3 and 21% in VP4. Within the VP2 molecule the conformation-dependent epitope area is again the least homologous, but the heterogeneity is more conspicuous than between the two IBDV strains, which is not surprising since IBDV and IPNV are serologically unrelated. The small ORF proteins have about 88% amino acid sequence homology between STC-IBDV and 002-73-IBDV, and 30% between each IBDV strain and Jasper-IPNV. There is no homology at all in the non-coding regions of IBDV and IPNV. These comparative sequence data will be useful for subgrouping the Birnaviridae family.

Amino Acid Sequence↗
PubMed1991

Complete nucleotide sequence and genetic organization of grapevine fanleaf nepovirus RNA1.

The nucleotide sequence of the genomic RNA1, 7342 nucleotides (nt) of grapevine fanleaf virus strain F13 (GFLV-F13) has been determined from cDNA clones. The complete sequence contained only one long open reading frame (ORF) of 6852 nucleotides extending from nucleotide 243 to 7101. The putative polyprotein encoded by this ORF is 2284 amino acids in length with an Mr of 253K. The location of genome-linked protein and comparison of the primary structure of the 253K polyprotein to that of other closely related viral proteins of the picronavirus-like family allows the proposal of a scheme for the genetic organization of GFLV-F13 RNA1. The primary structure of the polyprotein includes a putative RNA-dependent RNA polymerase of 92K and a cysteine protease of 25K. This protease shares not only major structural homologies, particularly in the substrate-binding pocket, with the trypsin-like serine proteases of other picorna-like viruses, but also their specificity in terms of cleavage. The large region of Mr 133K upstream of the VPg was found to contain at least two domains, one of which could be easily aligned with the NTP-binding sequence pattern and another which may have the characteristics of a protease cofactor. Thus, the 253K protein possesses the same general genetic organization as the corresponding protein of other picorna-like viruses.

Amino Acid Sequence↗
PubMed1992

Cleavage profiles of tobacco etch virus (TEV)-derived substrates mediated by precursor and processed forms of the TEV NIa proteinase.

Nucleotide sequences coding for proteins containing the tobacco etch virus (TEV) NIa proteinase were generated by polymerase chain reaction amplification and/or site-directed mutagenesis. These coding regions contained sequences for the proteinase alone or as part of higher Mr precursors. Following transcription and translation of these sequences in a cell-free system, the various polyproteins, all containing an active small nuclear inclusion protein (NIa) proteinase, were used to process a TEV substrate series. Most substrates were processed in a similar fashion by all proteolytic forms. However, one substrate which contained the TEV 50K/71K protein junction was differently processed by several of the polyproteins containing NIa proteinase. Substrates which previously had no identified TEV NIa proteinase cleavage sites also were tested and were not cleaved by any of the proteinase-containing polyprotein forms.

Amino Acid Sequence↗
PubMed1992

Complete nucleotide sequence and genetic organization of papaya ringspot virus RNA.

The complete nucleotide sequence of the RNA genome of papaya ringspot virus (PRSV) was determined from four overlapping cDNA clones and by direct sequencing of viral RNA. The genomic RNA is 10326 nucleotides in length, excluding the poly(A) tract, and contains one large open reading frame that starts at nucleotide positions 86 to 88 and ends at positions 10118 to 10120, encoding a polyprotein of 3344 amino acids. The highly conserved sequence AAAUAAAANANCUCAACACAACAUA at the 5' end of the RNA of PRSV and those of the other five reported potyviruses shows 80% similarity, suggesting that this region may play a common important role for potyvirus replication. Two cleavage sites of the polyprotein were determined by amino acid sequencing of the N termini of helper component (HC-Pro, amorphous inclusion) and cylindrical inclusion (CI) proteins. Other cleavage sites were predicted by analogy with the other potyviruses. The genetic organization of PRSV is similar to that of the other potyviruses except that the first protein processed from the N terminus of the polyprotein (NT protein) has an M(r) of 63K, 18K to 34K larger than those of the other potyviruses. The cleavage site for liberating the N terminus of the HC-Pro protein was found at the same location down-stream from the consensus sequence FI(V)VRG as that reported for tobacco vein mottling virus. The NT protein of potyviruses is the most variable and may be considered important for identification of individual potyviruses. The most conserved protein of potyviruses appears to be the NIb protein, the putative polymerase for the replication of the potyviral RNA. The genetic organization of PRSV RNA is tentatively proposed to be VPg-5' leader-63K NT-52K HC-Pro-46K-72K CI-6K-48K NIa-59K NIb-35K coat protein-3' non-coding region-poly(A) tract.

Amino Acid Sequence↗
PubMed1992

The nucleotide sequence of parsnip yellow fleck virus: a plant picorna-like virus.

The complete sequence of 9871 nucleotides (nts) of parsnip yellow fleck virus (PYFV; isolate P-121) was determined from cDNA clones and by direct sequencing of viral RNA. The RNA contains a large open reading frame between nts 279 and 9362 which encodes a polyprotein of 3027 amino acids with a calculated M(r) of 336212 (336K). A PYFV polyclonal antiserum reacted with the proteins expressed from phage carrying cDNA clones from the 5' half of the PYFV genome. Comparison of the polyprotein sequence of PYFV with other viral polyprotein sequences reveals similarities to the putative NTP-binding and RNA polymerase domains of cowpea mosaic comovirus, tomato black ring nepovirus and several animal picornaviruses. The 3' untranslated region of PYFV RNA is 509 nts long and does not have a poly(A) tail. The 3'-terminal 121 nts may form a stem-loop structure which resembles that formed in the genomic RNA of mosquito-borne flaviviruses.

Amino Acid Sequence↗
PubMed1992

The complete nucleotide sequence of RNA 1 of a German isolate of barley yellow mosaic virus and its comparison with a Japanese isolate.

The nucleotide sequence of RNA 1 of a German isolate of barley yellow mosaic virus has been determined and compared with a Japanese isolate of the same virus. The sequence identity is 93.6% at the nucleotide level and 96% at the amino acid level. Similar values have been found for the polyproteins of the RNA 2 of both isolates (95%). Both isolates show an RNA 1-encoded protein arrangement similar to that of potyviruses such as tobacco etch virus. In contrast, the polyproteins of the small RNAs (RNA 2) do not show such a similarity to the polyproteins of other potyviruses. However, there is a striking difference between the two isolates in the generally highly conserved active site of the RNA-dependent RNA polymerase. The German isolate exactly matches the consensus sequences for previously described potyviral RNA-dependent RNA polymerases, whereas the Japanese isolate does not.

Amino Acid Sequence↗
PubMed1994

Localization of viral protein X in simian immunodeficiency virus macaque strain and analysis of its packaging requirements.

Simian immunodeficiency virus (SIV) and human immunodeficiency virus type 2 (HIV-2) encode the accessory viral protein X (Vpx) known to be incorporated into virions in amounts comparable to those of the Gag proteins. The localization of Vpx within SIVmac-infected HUT-78 cells and SIVmac virions was studied by immunoelectron microscopy. Vpx appeared to be associated with extracellular virions as well as budding viral particles at the surface of infected cells. Immunolabelling of purified viral cores suggested that Vpx was a component of the amorphous material surrounding the core structure. Furthermore, a detergent insoluble fraction containing SIV core proteins was devoid of Vpx. To investigate the protein requirement for packaging of Vpx, BHK-21 cells were co-infected with vaccinia virus recombinants encoding Vpx and other SIV proteins able to assemble into virus-like particles. Analysis by immunoprecipitation of the extracellular particulate material as well as immunoelectron microscopy demonstrated that co-expression of Vpx with the Pr56gag polyprotein was sufficient for the formation of pseudo-virions containing Vpx. Virus-like particles that appeared upon expression of p16gag did not contain Vpx. The results suggest that Vpx is packaged into viral particles through its binding to the Gag polyprotein. The precise positioning of Vpx within the space separating the viral envelope from the core structure is postulated to result from the reorganization of viral proteins that occurs upon Gag polyprotein cleavage and budding.

Animals↗
PubMed1997

Proteolytic activity in vivo and encapsidation of recombinant human immunodeficiency virus type 1 proteinase expressed in baculovirus-infected cells.

The activity in vivo of HIV-1 proteinase (PR) was analysed in the baculovirus expression system, using eight different constructs of the prt gene under the control of polyhedrin (PH) promoters of various strengths. None of the active PRs was expressed in substantial quantities, and only PH-fused and/or non-functional PR mutants accumulated in high amounts in insect cells. However, enough PR activity was generated from a lengthened PR construct in insect cells to process Gag polyprotein substrate co-expressed in the same cells in trans. Fusion of the first 58 residues from the PH sequence to the PR N terminus did not significantly change its activity and specificity of cleavage of the Gag substrate. When analysed under mild denaturing conditions, PH-fused or unfused full-length PR point mutants, as well as PH-fused or unfused C-terminal deletion mutants, showed a propensity to multimerize, with a predominant occurrence of dimers. The incorporation of PR into Gag particles was studied using eight Gag-PR fusion constructs, all containing a non-functional PR mutant. The PR domain was fused to the C-terminal p6 domain of Gag (p6gag), or translated in frame with NCp7 (as in frameshifted Gag-Pol polyprotein) and followed by downstream sequences of increasing lengths from the Pol domain or the bacterial beta-galactosidase. The results suggested that the presence of the p6gag domain was detrimental to the encapsidation of polyprotein-embedded PR.

Animals↗
PubMed1999

The nine C-terminal residues of the grapevine fanleaf nepovirus movement protein are critical for systemic virus spread.

The grapevine fanleaf virus (GFLV) RNA2-encoded polyprotein P2 is proteolytically cleaved by the RNA1-encoded proteinase to yield protein 2A, 2B(MP) movement protein and 2C(CP) coat protein. To further investigate the role of the 2B(MP) and 2C(CP) proteins in virus movement, RNA2 was engineered by alternatively replacing the GFLV 2B(MP) and 2C(CP) genes with their counterparts from the closely related Arabis mosaic virus (ArMV). Transcripts of all chimeric RNA2s were able to replicate in Chenopodium quinoa protoplasts and form tubules in tobacco BY-2 protoplasts in the presence of the infectious transcript of GFLV RNA1. Virus particles were produced when the GFLV 2C(CP) gene was replaced with its ArMV counterpart, but systemic virus spread did not occur in C. quinoa plants. In addition, chimeric RNA2 containing the complete ArMV 2B(MP) gene was neither encapsidated nor infectious on plants, probably because polyprotein P2 was incompletely processed. However, chimeric RNA2 encoding ArMV 2B(MP), in which the nine C-terminal residues were those of GFLV 2B(MP), formed virus particles and were infectious in the presence of GFLV but not ArMV 2C(CP). These results suggest that the nine C-terminal residues of 2B(MP) must be of the same virus origin as the proteinase for efficient proteolytic processing of polyprotein P2 and from the same virus origin as the 2C(CP) for systemic virus spread.

Amino Acid Sequence↗
PubMed1999

Phylogenetic analysis of GB viruses A and C: evidence for cospeciation between virus isolates and their primate hosts.

GB viruses A and C (GBV-A and GBV-C) have been isolated from humans and non-human primates. Phylogenetic analysis based on full-length polyproteins suggests that these two viruses have a common ancestor. It has now been determined that analysis of subgenomic amino acid sequences in the E2 and NS5 regions of GBV-A and a 345 nucleotide segment in the 5' non-coding (5'NC) region was able to reproduce the phylogenetic relationships obtained by complete polyprotein sequences analysis. Using 5'NC sequences from databases, GBV-A isolates were discriminated into eight genetic groups, each one closely associated with specific primate hosts. Phylogenetic analyses performed on sequences from the epsilon-globin genes of primate hosts on one hand and complete polyprotein sequences from GBV-A and GBV-C isolates on the other suggest that a mechanism of cospeciation could be involved in virus evolution over a period of 35 million years.

Animals↗
PubMed2001

The 'cleavage' activities of foot-and-mouth disease virus 2A site-directed mutants and naturally occurring '2A-like' sequences.

The 2A/2B cleavage of aphtho- and cardiovirus 2A polyproteins is mediated by their 2A proteins 'cleaving' at their own C termini. We have analysed this activity using artificial reporter polyprotein systems comprising green fluorescent protein (GFP) linked via foot-and-mouth disease virus (FMDV) 2A to beta-glucuronidase (GUS) -- forming a single, long, open reading frame. Analysis of the distribution of radiolabel showed a high proportion of the in vitro translation products (approximately 90%) were in the form of the 'cleavage' products GUS and [GFP2A]. Alternative models have been proposed to account for the 'cleavage' activity: proteolysis by a host-cell proteinase, autoproteolysis or a translational effect. To investigate the mechanism of this cleavage event constructs encoding site-directed mutant and naturally occurring '2A-like' sequences were used to program in vitro translation systems and the gel profiles analysed. Analysis of site-directed mutant 2A sequences showed that 'cleavage' occurred in constructs in which all the candidate nucleophilic residues were substituted -- with the exception of aspartate-12. This residue is not, however, conserved amongst all functional '2A-like' sequences. '2A-like' sequences were identified within insect virus polyproteins, the NS34 protein of type C rotaviruses, repeated sequences in Trypanosoma spp. and a eubacterial alpha-glucosiduronasesequence(Thermatoga maritima aguA). All of the 2A-like sequences analysed were active (to various extents), other than the eubacterial alpha-glucosiduronase 2A-like sequence. This method of control of protein biogenesis may well not, therefore, be confined to members of the PICORNAVIRIDAE: Taken together, these data provide additional evidence that neither FMDV 2A nor '2A-like' sequences are autoproteolytic elements.

Amino Acid Sequence↗
PubMed2002

Characterization and complete nucleotide sequence of Strawberry mottle virus: a tentative member of a new family of bipartite plant picorna-like viruses.

An isolate of Strawberry mottle virus (SMoV) was transferred from Fragaria vesca to Nicotiana occidentalis and Chenopodium quinoa by mechanical inoculation. Electron micrographs of infected tissues showed the presence of isometric particles of approximately 28 nm in diameter. SMoV-associated tubular structures were also conspicuous, particularly in the plasmodesmata of C. quinoa. DsRNA extraction of SMoV-infected N. occidentalis yielded two bands of 6.3 and 7.8 kbp which were cloned and sequenced. Gaps in the sequence, including the 5' and 3' ends, were filled using RT-PCR and RACE. The genome of SMoV was found to consist of RNA1 and RNA2 of 7036 and 5619 nt, respectively, excluding a poly(A) tail. Each RNA encodes one polyprotein and has a 3' non-coding region of approximately 1150 nt. The polyprotein of RNA1 contains regions with identities to helicase, viral genome-linked protein, protease and polymerase (RdRp), and shares its closest similarity with RNA1 of the tentative nepovirus Satsuma dwarf virus (SDV). The polyprotein of RNA2 displayed some similarity to the large coat protein domain of SDV and related viruses. Phylogenetic analysis of the RdRp region showed that SMoV falls into a separate group containing SDV, Apple latent spherical virus, Naval orange infectious mottling virus and Rice tungro spherical virus. Given the size of RNA2 and the presence of a long 3' non-coding region, SMoV is more typical of a nepovirus, although atypically for a nepovirus it is aphid transmissible. We propose that SMoV is a tentative member of an SDV-like lineage of picorna-like viruses.

3' Untranslated Regions↗
PubMed1997

A cell-associated protein complex of Porphyromonas gingivalis W50 composed of Arg- and Lys-specific cysteine proteinases and adhesins.

Porphyromonas gingivalis has been associated with the development of adult periodontitis and cysteine proteinases with trypsin-like specificity have been implicated as major virulence factors. We have extracted the major cell-associated trypsin-like proteolytic activity of P. gingivalis W50 using mild sonication. Anion-exchange and gel-filtration FPLC of the sonicate revealed that Arg- and Lys-specific proteinase activity was associated with a 300 kDa complex which could be dissociated into seven bands (48, 45, 44, 39, 27, 17 and 15 kDa) by SDS-PAGE with the 44 kDa band containing two different proteins as shown by N-terminal sequence analysis. On further chromatography of the 300 kDa complex on Arg-Sepharose the majority of the complex eluted from the affinity column as an undissociated complex. However, a small amount dissociated such that the Lys- and Arg-specific activities could be separated by eluting first with lysine then arginine, respectively. The 45 kDa protein of the complex was purified by further anion-exchange FPLC in the presence of octyl-beta-D-glucopyranoside and was shown to be an Arg-specific, thiol-activated, calcium-stabilized cysteine proteinase. The 48 kDa protein was also further purified in a similar fashion and shown to be a Lys-specific cysteine proteinase that was not inhibited by EDTA. The two 44 kDa and the 39, 27, 17 and 15 kDa proteins of the complex exhibit amino acid sequence homology and are proposed to be haemagglutinins/adhesins. The 45 kDa Arg-specific proteinase and one of the 44 kDa adhesins as well as the 15, 17 and 27 kDa adhesins are processed from the single polyprotein encoded by the gene designated prtR, with all proteins preceded by an Arg or Lys residue within the polyprotein. Similarly, the 48 kDa Lys-specific proteinase, the 39 and 15 kDa adhesins as well as the other 44 kDa adhesin of the 300 kDa complex are encoded by a single gene designated prtK, with all proteins preceded by an Arg or Lys residue within the polyprotein. The 39, 15 and 44 kDa adhesins of PrtK all exhibit high homology with the 44, 15, 17 and 27 kDa adhesins encoded by prtR, particularly the 15 kDa proteins which are identical. The cell-associated proteinase-adhesin complex, designated PrtR-PrtK, is therefore composed of the two gene products, the mature PrtR (160 kDa) and mature PrtK (163 kDa) that are further proteolytically processed (most likely autolytically) to release proteinase and adhesin domains that remain non-covalently associated. The fully processed PrtR-PrtK complex comprises the cysteine proteinases-PrtR45 and PrtK48 and seven sequence-related adhesin molecules, PrtR44, PrtR15, PrtR17, PrtR27 and PrtK39, PrtK15 and PrtK44. We propose that this proteinase-adhesin complex is a major virulence factor for P. gingivalis involved in the evasion of host defence and in the assimilation of haem and peptides.

Adhesins, Bacterial↗