Analysis and phylogeny of small heat shock proteins from marine viruses and their cyanobacteria host

• Published in: PloS one Vol. 8; no. 11; p. e81207
• Main Authors: Maaroufi, Halim, Tanguay, Robert M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12-11-2013; Public Library of Science (PLoS)
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Amino acids; Analysis; Anchoring; Animals; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacteriophages - classification; Bacteriophages - genetics; Biochemistry; Crystallin; Cyanobacteria; Cyanobacteria - classification; Cyanobacteria - genetics; Cyanobacteria - virology; Eukaryotes; Genes; Genomes; Heat shock proteins; Heat-Shock Proteins, Small - chemistry; Heat-Shock Proteins, Small - genetics; Hydrophobic and Hydrophilic Interactions; Models, Molecular; Molecular Sequence Data; Oligomerization; Oligomers; Phages; Phylogenetics; Phylogeny; Prochlorococcus; Prokaryotes; Protein Conformation; Protein Interaction Domains and Motifs; Proteins; Sequence Alignment; Small heat shock proteins; Static Electricity; Stress proteins; Synechococcus; Viral Proteins - chemistry; Viral Proteins - genetics; Viruses; Canada; Quebec Canada
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0081207

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.