title: The mouse B cell-specific mb-1 gene encodes an immunoreceptor tyrosine-based activation motif (ITAM) protein that may be evolutionarily conserved in diverse species by purifying selection.
abstract: The B-lymphocyte accessory molecule Ig-alpha (Ig-α) is encoded by the mouse B cell-specific gene (mb-1), and along with the Ig-beta (Ig-β) molecule and a membrane bound immunoglobulin (mIg) makes up the B-cell receptor (BCR). Ig-α and Ig-β form a heterodimer structure that upon antigen binding and receptor clustering primarily initiates and controls BCR intracellular signaling via a phosphorylation cascade, ultimately triggering an effector response. The signaling capacity of Ig-α is contained within its immunoreceptor tyrosine-based activation motif (ITAM), which is also a key component for intracellular signaling initiation in other immune cell-specific receptors. Although numerous studies have been devoted to the mb-1 gene product, Ig-α, and its signaling mechanism, an evolutionary analysis of the mb-1 gene has been lacking until now. In this study, mb-1 coding sequences from 19 species were compared using Bayesian inference. Analysis revealed a gene phylogeny consistent with an expected species divergence pattern, clustering species from the primate order separate from lower mammals and other species. In addition, an overall comparison of non-synonymous and synonymous nucleotide mutational changes suggests that the mb-1 gene has undergone purifying selection throughout its evolution.
authors.affiliation: Department of Biology, California State University Northridge, 18111 Nordhoff St, Northridge, CA 91330-8303, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Sims
authors.forename: Virginia Oberholzer
authors.initials: VO
authors.lastname: Vandergon
authors.forename: Cindy S
authors.initials: CS
authors.lastname: Malone
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D051925:CD79 Antigens / Q000235:genetics* / Q000378:metabolism; D019295:Computational Biology; D017124:Conserved Sequence / Q000235:genetics; D019143:Evolution, Molecular; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010802:Phylogeny; D011947:Receptors, Antigen, B-Cell / Q000235:genetics*; D012641:Selection, Genetic; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D013045:Species Specificity
chemical_list: D051925:CD79 Antigens; C497882:Cd79a protein, mouse; D011947:Receptors, Antigen, B-Cell