The evolution of lysozyme and alpha-lactalbumin.
From the analysis of phylogenetic trees constructed from the amino acid sequences and metal-binding properties of various lysozymes c and alpha-lactalbumins, it was found that before the divergence of the lineages of birds and mammals, calcium-binding lysozyme diverged from non-calcium-binding lysozyme. alpha-Lactalbumin evolved from the calcium-binding lysozyme along the mammalian lineage after the divergence of birds and mammals. Rapid evolution took place, not in the process of acquisition of the activity of alpha-lactalbumin, but after the loss of lysozyme activity, due to the change in the distribution of selective pressure on each amino acid site. A general process for the change in function of a protein during evolution is suggested to be as follows: after duplication of the gene, one of their protein products acquires a new function, besides that already present; the old function is eventually lost.
Nitta
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K
Department of Polymer Science, Faculty of Science, Hokkaido University, Japan.
Sugai
S
S
D000595:Amino Acid Sequence; D000818:Animals; D017317:Annexin A6; D001483:Base Sequence; D005075:Biological Evolution; D001717:Birds; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000502:physiology; D006801:Humans; D007768:Lactalbumin / Q000235:genetics* / Q000502:physiology; D008322:Mammals; D009036:Moths; D009113:Muramidase / Q000235:genetics* / Q000502:physiology; D009154:Mutation; D013045:Species Specificity
D017317:Annexin A6; D002135:Calcium-Binding Proteins; D007768:Lactalbumin; D009113:Muramidase