Identification of a positively evolving putative binding region with increased variability in posttranslational motifs in zonadhesin MAM domain 2.
Positive selection has been shown to be pervasive in sex-related proteins of many metazoan taxa. However, we are only beginning to understand molecular evolutionary processes on the lineage to humans. To elucidate the evolution of proteins involved in human reproduction, we studied the sequence evolution of MAM domains of the sperm-ligand zonadhesin in respect to single amino acid sites, solvent accessibility, and posttranslational modification. GenBank-data were supplemented by new cDNA-sequences of a representative non-human primate panel. Solvent accessibility predictions identified a probably exposed fragment of 30 amino acids belonging to MAM domain 2 (i.e., MAM domain 3 in mouse). The fragment is characterized by significantly increased rate of positively selected amino acid sites and exhibits high variability in predicted posttranslational modification, and, thus, might represent a binding region in the mature protein. At the same time, there is a significant coincidence of positively selected amino acid sites and non-conserved posttranslational motifs. We conclude that the binding specificity of zonadhesin MAM domains, especially of the presumed epitope, is achieved by positive selection at the level of single amino acid sites and posttranslational modifications, respectively.
Herlyn
Holger
H
Institute of Anthropology, University of Mainz, Germany. herlyn@uni-mainz.de
Zischler
Hans
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D014644:Genetic Variation; D006031:Glycosylation; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases; D012097:Repressor Proteins / Q000235:genetics*; D012641:Selection, Genetic; D017386:Sequence Homology, Amino Acid; D013079:Sperm Maturation / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
C408904:Atf7ip protein, mouse; D008565:Membrane Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C096806:zonadhesin; C486000:Stk16 protein, mouse; D017346:Protein Serine-Threonine Kinases