La. Omtvedt et al., THE AMINO-ACID-SEQUENCE OF THE GLYCOSYLATED AMYLOID IMMUNOGLOBULIN LIGHT-CHAIN PROTEIN AL MS, Scandinavian journal of immunology, 45(5), 1997, pp. 551-556
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.