Primary structure of rat lysozyme

Abstract

The primary structure of rat lysozyme was determined. The chymotryptic peptides from the reduced and carboxymethylated protein were sequenced and aligned by homology with the sequence of human lysozyme. Overlaps were confirmed by partial structures of tryptic peptides and an automatic sequencer run on the whole protein. By comparing this lysozyme sequence with those of human and baboon and taking into account paleontological estimates of the times of divergence of these species from one anothr, an approximate estimate of the average rate of lysozyme evolution was made. This rate is not significantly different from the average rate of lactalbumin evolution in mammals.sbd.a finding which is at variance with Dickerson''s and Dayhoff''s conclusion that lactalbumin evolution was faster than lysozyme evolution. Thus, the the gene duplication event responsible for the origin of lactalbumin from lysozyme may be more ancient than is generally supposed. Comparison of the rates of lysozyme evolution in rodents and primates suggests that generation time is not a key factor in lysozyme evolution.