COMPLETE AMINO-ACID-SEQUENCE DETERMINATIONS DEMONSTRATE IDENTITY OF THE URINARY BENCE-JONES PROTEIN (BJP-DIA) AND THE AMYLOID FIBRIL PROTEIN (AL-DIA) IN A CASE OF AL-AMYLOIDOSIS

The complete primary structures of both the main amyloid fibril protei n component (AL-DIA) and the soluble Bence Jones protein (BJP-DIA) obt ained from the same patient with AL-amyloidosis are reported for the f irst time. The amino acid sequences were determined by automated Edman degradation following proteolytic digestion of the isolated proteins and HPLC separation of the resulting fragments and by amino-terminal s equencing after treatment with pyroglutamate aminopeptidase. Sequencin g data were confirmed by amino acid analysis and plasma desorption mas s spectrometry (PDMS). Molecular weights of the complete proteins were determined by laser desorption mass spectrometry. The amyloid fibril preparation contained a complete monoclonal lambda-immunoglobulin ligh t chain (subgroup 1.2) as well as different-sized fragments thereof wh ich were identified by immunoblotting and amino-terminal sequencing fo llowing immobilization of electrophoretically-separated proteins on po ly(vinylidene difluoride) (PVDF) membranes. The soluble urinary Bence Jones protein (BJP-DIA) was a dimer of monoclonal L-chains with a prim ary structure identical to that of the amyloid L-chain (AL-DIA) and th us represented the amyloid precursor protein.