title: Analysis and phylogeny of small heat shock proteins from marine viruses and their cyanobacteria host.
abstract: Small heat shock proteins (sHSPs) are oligomeric stress proteins characterized by an α-crystallin domain (ACD) surrounded by a N-terminal arm and C-terminal extension. Publications on sHSPs have reported that they exist in prokaryotes and eukaryotes but, to our knowledge, not in viruses. Here we show that sHSPs are present in some cyanophages that infect the marine unicellular cyanobacteria, Synechococcus and Prochlorococcus. These phage sHSPs contain a conserved ACD flanked by a relatively conserved N-terminal arm and a short C-terminal extension with or without the conserved C-terminal anchoring module (CAM) L-X-I/V, suggested to be implicated in the oligomerization. In addition, cyanophage sHSPs have the signature pattern, P-P-[YF]-N-[ILV]-[IV]-x(9)-[EQ], in the predicted β2 and β3 strands of the ACD. Phylogenetically, cyanophage sHSPs form a monophyletic clade closer to bacterial class A sHSPs than to cyanobacterial sHSPs. Furthermore, three sHSPs from their cellular host, Synechococcus, are phylogenetically close to plants sHSPs. Implications of evolutionary relationships between the sHSPs of cyanophages, bacterial class A, cyanobacteria, and plants are discussed.
authors.affiliation: Plate-forme de bio-informatique and Institut de biologie intégrative et des systèmes (IBIS), Université Laval, Quebec, Canada.
authors.forename: Halim
authors.initials: H
authors.lastname: Maaroufi
authors.forename: Robert M
authors.initials: RM
authors.lastname: Tanguay
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001435:Bacteriophages / Q000145:classification / Q000235:genetics*; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics* / Q000821:virology; D050888:Heat-Shock Proteins, Small / Q000737:chemistry / Q000235:genetics*; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D016415:Sequence Alignment; D055672:Static Electricity; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D050888:Heat-Shock Proteins, Small; D014764:Viral Proteins