Comparison of archaeal and bacterial genomes: computer analysis of protein sequences predicts novel functions and suggests a chimeric origin for the archaea.

摘要: Protein sequences encoded in three complete bacterial genomes, those of Haemophilus influenzae, Mycoplasma genitalium and Synechocystis sp., the first available archaeal genome sequence, that Methanococcus jannaschii, were analysed using BLAST2 algorithm methods for amino acid motif detection. Between 75% 90% predicted proteins each genomes 73% M. jannaschii showed significant sequence similarity to from other species. The fraction containing regions conserved over long phylogenetic distances is nearly same close 70%. Functions 70-85% about 70% with varying precision. This contrasts previous report more than half have no homologues shows that, sensitive detailed analysis motifs, become as amenable meaningful interpretation by computer genomes. motifs resulted prediction a number previously undetected functions identification novel protein families. In spite generally high conservation sequences, orthologues 25% or less genes detected individual completely sequenced genome, supporting uniqueness archaea distinct domain life. About 53% belong families paralogues, similar bacteria larger such sp. Escherichia coli, but higher H. which has approximately jannaschii. Certain groups proteins, e.g. molecular chaperones DNA repair enzymes, thought be ubiquitous represented minimal gene set derived comparison, are missing indicating massive non-orthologous displacement responsible essential functions. An unexpectedly large products, 44%, significantly eukaryotic compared 13% their closest (the rest show level homologues). Proteins involved translation, transcription, replication secretion most closely related whereas metabolic metabolite uptake systems, enzymes cell wall biosynthesis many uncharacterized appear 'bacterial'. A prevalence apparent origin was observed among currently distantly genus, Sulfolobus. It likely evolution included at least one major merger between ancestral cells lineage leading nucleocytoplasm.