THE AMINO-ACID-SEQUENCE OF THE GLYCOSYLATED AMYLOID IMMUNOGLOBULIN LIGHT-CHAIN PROTEIN AL MS

The authors report on the amino acid sequence of the glycosylated amyl oid protein AL MS. The amyloid fibrils were extracted from the spleen of a patient (MS.) with amyloidosis. The protein AL MS was purified fr om the amyloid fibrils by gel filtration. SDS-PAGE performed on the pu rified protein material showed glycosylated protein bands in the range of 22 to 32kDa, corresponding to polymerization of N-terminal fragmen ts. The protein was characterized by amino acid analysis and Edman deg radation. Tryptic digest combined with Staphylococcal V8 protease, chy motrypsin and pyroglutamate aminopeptidase digestion, as well as cleav age with BNPS-skatole, established the complete amino acid sequence of 168 residues. The protein was compared to other proteins in the SWISS PROT databank, showing homology with the immunoglobulin light chain va riable subgroup lambda I. AL MS showed some unique amino acid substitu tions. Highly conserved residues Gly(57) and Arg(61), were exchanged t o arginine and glutamine, respectively, possibly altering the three-di mensional structure of the protein.