CHARACTERIZATION OF 3 TYPES OF HUMAN ALPHA(S1)-CASEIN MESSENGER-RNA TRANSCRIPTS

Here we report the molecular cloning and sequencing of three types of human alpha(s1)-casein transcripts and present evidence indicating tha t exon skipping is responsible for deleted mRNA transcripts. The large st transcript comprised 981 bp encoding a signal peptide of 15 amino a cids followed by the mature alpha(s1)-casein sequence of 170 amino aci ds. Human alpha(s1)-casein has been reported to exist naturally as a m ultimer in complex with kappa-casein in mature human milk, thereby bei ng unique among alpha(s1)-caseins [Rasmussen, Due and Petersen (1995) Comp. Biochem. Physiol., in the press]. The present demonstration of t hree cysteines in the mature protein provides a molecular explanation of the interactions in this complex. Tissue-specific expression of hum an alpha(s1)-casein was indicated by Northern-blot analysis. In additi on, two cryptic exons were localized in the bovine alpha(s1)-casein ge ne.