title: Sequencing of amphioxus PSMB5/8 gene and phylogenetic position of agnathan sequences.
abstract: Reanalyses of vertebrate PSMB5 and PSMB8 genes were conducted with a newly obtained amphioxus sequence. The phylogenetic analysis indicated that the amphioxus sequence is an outgroup of both vertebrate PSMB5 and PSMB8 genes. The agnathan sequences were previously thought to be closer to PSMB5 than PSMB8 sequences. However, in this study the phylogenetic trees supported the clustering of agnathan sequences with PSMB8 rather than with PSMB5 sequences. In the alignment there are many sites in which the agnathan sequences are more similar to PSMB5 than PSMB8 sequences. Parsimony analysis showed that the amino acid pattern at these sites could be explained by one substitution on the ancestral branch leading to the jawed vertebrate PSMB8 cluster. The number of substitutions required at these sites was the same for different tree topologies with respect to the position of agnathans. The phylogenetic analyses of PSMB6/PSMB9 and PSMB7/PSMB10 genes indicated that all the interferon-gamma-inducible forms have evolved two to three times faster than the housekeeping forms in the jawed vertebrate lineage. Hence although the agnathan sequences cluster with the PSMB8 sequences, they have a slower rate of evolution similar to that of the housekeeping forms, and may be functioning as housekeeping forms.
authors.affiliation: Max-Planck-Institut für Biologie, Abteilung Immungenetik, Corrensstrasse 42, 72076 Tübingen, Germany. naoko.takezaki@tuebingen.mpg.de
authors.forename: Naoko
authors.initials: N
authors.lastname: Takezaki
authors.forename: Zofia
authors.initials: Z
authors.lastname: Zaleska-Rutczynska
authors.forename: Felipe
authors.initials: F
authors.lastname: Figueroa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D003546:Cysteine Endopeptidases / Q000235:genetics*; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D010450:Endopeptidases / Q000235:genetics; D007798:Lampreys / Q000235:genetics*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D029961:Zebrafish Proteins
chemical_list: D018076:DNA, Complementary; D009097:Multienzyme Complexes; D011506:Proteins; C121057:Psmb11 protein, zebrafish; C121061:Psmb9A protein, zebrafish; D029961:Zebrafish Proteins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex; C121055:Psmb7 protein, zebrafish