title: The determinants of the oligomeric structure in Hsp16.5 are encoded in the alpha-crystallin domain.
abstract: The determinants of the oligomeric assembly of Hsp16.5, a small heat-shock protein (sHSP) from Methanococcus jannaschii, were explored via site-directed truncation and site-directed spin labeling. For this purpose, subunit contacts around the two-, three- and four-fold symmetry axes were fingerprinted using patterns of proximities between nitroxide spin labels introduced at selected sites. The lack of change in this fingerprint in an N-terminal truncation of the protein demonstrates that the interactions are encoded in the alpha-crystallin domain. In contrast, the truncation of the N-terminal domain of Mycobacterium tuberculosis Hsp16.3, a bacterial sHSP with an equally short N-terminal region, results in the dissociation of the oligomer to a trimer. These results, in conjunction with those from previous truncation studies in mammalian sHSP, suggest that as the alpha-crystallin domain evolved to encode a smaller basic unit than the overall oligomer, the control of the assembly and dynamics of the oligomeric structure became encoded in the N-terminal domain.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, 1161 21st Ave. South, 741 Light Hall, Nashville, TN 37232, USA.
authors.forename: Hanane A
authors.initials: HA
authors.lastname: Koteiche
authors.forename: Hassane S
authors.initials: HS
authors.lastname: Mchaourab
mesh_terms: D019843:Archaeal Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003459:Crystallins / Q000235:genetics*; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000235:genetics; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D017017:Methanococcus; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013113:Spin Labels
chemical_list: D019843:Archaeal Proteins; D003459:Crystallins; C113795:HSP16.5 protein, Methanococcus jannaschii; D006360:Heat-Shock Proteins; D013113:Spin Labels