title: Novel chaperonins in a prokaryote.
abstract: Group II chaperonins belong to the Hsp60 family occurring in archaea and eukaryotes. The archaeal chaperonins build the thermosome, which is similar to the eukaryotic CCT (chaperonin-containing TCP-1). Eukaryotes have eight subunits, and up until now, it was thought that archaea had between one and three subunits, depending on the species. We now report two novel subunits, termed Hsp60-4 and Hsp60-5, in the archaeon Methanosarcina acetivorans, which also has Hsp60-1, Hsp60-2, and Hsp60-3 with orthologs in Methanosarcinae. Hsp60-4 and Hsp60-5 occur only in M. acetivorans, which makes this organism unique in that it has the highest number of chaperonin subunits ever described for an archaeon. Evolutionary analysis suggests that either Hsp60-4 or Hsp60-5 paralogs have arisen by gene duplication with vastly increased accepted substitution rates or that they represent ancestral types found only in this species.
authors.affiliation: Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, 21202, USA.
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Maeder
authors.forename: Alberto J L
authors.initials: AJ
authors.lastname: Macario
authors.forename: Everly
authors.initials: E
authors.lastname: Conway de Macario
mesh_terms: D000595:Amino Acid Sequence; D018834:Chaperonin 60 / Q000235:genetics*; D018833:Chaperonins / Q000235:genetics*; D019295:Computational Biology; D030561:Databases, Nucleic Acid; D019143:Evolution, Molecular; D016013:Likelihood Functions; D017020:Methanosarcina / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D016415:Sequence Alignment; D013045:Species Specificity
chemical_list: D018834:Chaperonin 60; D018833:Chaperonins