title: In Vitro Structural and Functional Characterization of the Small Heat Shock Proteins (sHSP) of the Cyanophage S-ShM2 and Its Host, Synechococcus sp. WH7803.
abstract: We previously reported the in silico characterization of Synechococcus sp. phage 18 kDa small heat shock protein (HspSP-ShM2). This small heat shock protein (sHSP) contains a highly conserved core alpha crystalline domain of 92 amino acids and relatively short N- and C-terminal arms, the later containing the classical C-terminal anchoring module motif (L-X-I/L/V). Here we establish the oligomeric profile of HspSP-ShM2 and its structural dynamics under in vitro experimental conditions using size exclusion chromatography (SEC/FPLC), gradient native gels electrophoresis and dynamic light scattering (DLS). Under native conditions, HspSP-ShM2 displays the ability to form large oligomers and shows a polydisperse profile. At higher temperatures, it shows extensive structural dynamics and undergoes conformational changes through an increased of subunit rearrangement and formation of sub-oligomeric species. We also demonstrate its capacity to prevent the aggregation of citrate synthase, malate dehydrogenase and luciferase under heat shock conditions through the formation of stable and soluble hetero-oligomeric complexes (sHSP:substrate). In contrast, the host cyanobacteria Synechococcus sp. WH7803 15 kDa sHSP (HspS-WH7803) aggregates when in the same conditions as HspSP-ShM2. However, its solubility can be maintained in the presence of non-ionic detergent Triton™X-100 and forms an oligomeric structure estimated to be between dimer and tetramer but exhibits no apparent inducible structural dynamics neither chaperon-like activity in all the assays and molar ratios tested. SEC/FPLC and thermal aggregation prevention assays results indicate no formation of hetero-oligomeric complex or functional interactions between both sHSPs. Taken together these in vitro results portray the phage HspSP-ShM2 as a classical sHSP and suggest that it may be functional at the in vivo level while behaving differently than its host amphitropic sHSP.
authors.affiliation: Laboratoire de Biologie Cellulaire et Moléculaire, Institut de Biologie Intégrative et des Systémes (IBIS) and PROTEO, Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de Médecine, Québec, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Bourrelle-Langlois
authors.affiliation: Laboratoire de Biologie Cellulaire et Moléculaire, Institut de Biologie Intégrative et des Systémes (IBIS) and PROTEO, Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de Médecine, Québec, Canada.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Morrow
authors.affiliation: IMPMC UMR7590, CNRS/Sorbonne-Universités, UPMC/IRD/MNHN Paris 6, Paris, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Finet
authors.affiliation: Laboratoire de Biologie Cellulaire et Moléculaire, Institut de Biologie Intégrative et des Systémes (IBIS) and PROTEO, Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de Médecine, Québec, Canada.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Tanguay
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001435:Bacteriophages / Q000737:chemistry* / Q000378:metabolism; D050888:Heat-Shock Proteins, Small / Q000737:chemistry* / Q000378:metabolism; D066329:Protein Aggregates; D011487:Protein Conformation; D055503:Protein Multimerization; D012995:Solubility; D046940:Synechococcus / Q000737:chemistry* / Q000378:metabolism / Q000821:virology*; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D050888:Heat-Shock Proteins, Small; D066329:Protein Aggregates; D014764:Viral Proteins