The amino acid substitution in albumin Roma: 321 Glu → Lys

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Abstract
Albumin Roma is an electrophoretically slow moving genetic variant of human serum albumin found in 22 unrelated families. The protein was isolated from the serum of a healthy, heterozygous subject. Analysis of CNBr fragments by isoelectric focusing allowed us to localize the mutation to fragment CNBr IV (residues 299–329). This fragment was isolated on a preparative scale by RP‐HPLC and subjected to tryptic digestion. Sequential analysis of two abnormal tryptic peptides, purified by RP‐HPLC, revealed that the variant arises from the substitution of glutamic acid 321 by lysine. This amino acid replacement, probably resulting from a point mutation in the structural gene, causes a change in the net charge of +2 units which is in keeping with the decreased electrophoretic mobility of the native protein.