title: Molecular evolution of cyclin proteins in animals and fungi.
abstract: BACKGROUND
  The passage through the cell cycle is controlled by complexes of cyclins, the regulatory units, with cyclin-dependent kinases, the catalytic units. It is also known that cyclins form several families, which differ considerably in primary structure from one eukaryotic organism to another. Despite these lines of evidence, the relationship between the evolution of cyclins and their function is an open issue. Here we present the results of our study on the molecular evolution of A-, B-, D-, E-type cyclin proteins in animals and fungi.
  
  
  RESULTS
  We constructed phylogenetic trees for these proteins, their ancestral sequences and analyzed patterns of amino acid replacements. The analysis of infrequently fixed atypical amino acid replacements in cyclins evidenced that accelerated evolution proceeded predominantly during paralog duplication or after it in animals and fungi and that it was related to aromorphic changes in animals. It was shown also that evolutionary flexibility of cyclin function may be provided by consequential reorganization of regions on protein surface remote from CDK binding sites in animal and fungal cyclins and by functional differentiation of paralogous cyclins formed in animal evolution.
  
  
  CONCLUSIONS
  The results suggested that changes in the number and/or nature of cyclin-binding proteins may underlie the evolutionary role of the alterations in the molecular structure of cyclins and their involvement in diverse molecular-genetic events.
authors.affiliation: Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Lavrentyev ave,, 10, Novosibirsk, Russia. genkvg@gmail.com
authors.forename: Konstantin V
authors.initials: KV
authors.lastname: Gunbin
authors.forename: Valentin V
authors.initials: VV
authors.lastname: Suslov
authors.forename: Igor I
authors.initials: II
authors.lastname: Turnaev
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Afonnikov
authors.forename: Nikolay A
authors.initials: NA
authors.lastname: Kolchanov
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016213:Cyclins / Q000737:chemistry / Q000235:genetics*; D056890:Eukaryota / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D005658:Fungi / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D016213:Cyclins; D005656:Fungal Proteins