title: Genealogy of the alpha-crystallin--small heat-shock protein superfamily.
abstract: Sequences of 40 very diverse representatives of the alpha-crystallin-small heat-shock protein (alpha-Hsp) superfamily are compared. Their characteristic C-terminal 'alpha-crystallin domain' of 80-100 residues contains short consensus sequences that are highly conserved from prokaryotes to eukaryotes. There are, in addition, some positions that clearly distinguish animal from non-animal alpha-Hsps. The alpha-crystallin domain is predicted to consist of two hydrophobic beta-sheet motifs, separated by a hydrophilic region which is variable in length. Combination of a conserved alpha-crystallin domain with a variable N-terminal domain and C-terminal extension probably modulates the properties of the various alpha-Hsps as stress-protective and structural oligomeric proteins. Phylogeny reconstruction indicates that multiple alpha-Hsps were already present in the last common ancestor of pro- and eukaryotes. It is suggested that during eukaryote evolution, animal and non-animal alpha-Hsps originated from different ancestral gene copies. Repeated gene duplications gave rise to the multiple alpha-Hsps present in most organisms.
authors.affiliation: Department of Biochemistry, University of Nijmegen, The Netherlands. w.dejong@bioch.kun.NL
authors.forename: W W
authors.initials: WW
authors.lastname: de Jong
authors.forename: G J
authors.initials: GJ
authors.lastname: Caspers
authors.forename: J A
authors.initials: JA
authors.lastname: Leunissen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D003459:Crystallins / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D015870:Gene Expression; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008322:Mammals; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D014714:Vertebrates
chemical_list: D003459:Crystallins; D006360:Heat-Shock Proteins