alpha-Lactalbumins and lysozymes.
Lysozyme is ubiquitous in a variety of tissues and secretions. Chick-type (c-type) lysozymes lyse the cell walls of certain bacteria. In contrast, alpha-lactalbumin appears to occur only in mammalian milk and colostrum. It has the unusual property of acting as a modifier protein to modify the action of galactosyl transferase to a lactose synthase. Both proteins have diverged from a common ancestor. This is reflected in the striking relationship between their amino acid sequences, and the high conservation of disulfide bridges, their intron-exon organization, and three-dimensional structures. In studying their evolutionary relationships some important differences are noted, e.g., all alpha-lactalbumins strongly bind Ca(II), but only some c-type lysozymes do so. These properties point the way to future investigations that are necessary before firm conclusions can be made about their evolutionary history.
McKenzie
H A
HA
School of Chemistry, University College, University of New South Wales, Australian Defence Force Academy, Canberra, Australia.
D000818:Animals; D002240:Carbohydrate Sequence; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D005700:Galactosyltransferases / Q000378:metabolism; D007768:Lactalbumin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007788:Lactose Synthase / Q000378:metabolism; D008892:Milk / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary
D007768:Lactalbumin; D005700:Galactosyltransferases; D007788:Lactose Synthase; D009113:Muramidase