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The amino acid sequence of the glycosylated amyloid immunoglobulin light chain protein AL MS
L A Omtvedt1, G Husby, G G Cornwell
1Department of Biochemistry/Biotechnology Centre of Oslo, University of Oslo, Norway.
Abstract:
The authors report on the amino acid sequence of the glycosylated amyloid protein AL MS. The amyloid fibrils were extracted from the spleen of a patient (MS.) with amyloidosis. The protein AL MS was purified from the amyloid fibrils by gel filtration. SDS-PAGE performed on the purified protein material showed glycosylated protein bands in the range of 22 to 32 kDa, corresponding to polymerization of N-terminal fragments. The protein was characterized by amino acid analysis and Edman degradation. Tryptic digest combined with Staphylococcal V8 protease, chymotrypsin and pyroglutamate aminopeptidase digestion, as well as cleavage with BNPS-skatole, established the complete amino acid sequence of 168 residues. The protein was compared to other proteins in the SWISSPROT databank, showing homology with the immunoglobulin light chain variable subgroup lamda I. AL MS showed some unique amino acid substitutions. Highly conserved residues Gly(57) and Arg(61), were exchanged to arginine and glutamine, respectively, possibly altering the three- dimensional structure of the protein.
Insights
Researchers determined the amino acid sequence of glycosylated amyloid protein AL MS from a patient with amyloidosis. This protein shows homology to immunoglobulin light chains but has unique substitutions that may alter its structure.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Chemistry
Background:
- Amyloidosis is a disease caused by the buildup of amyloid fibrils.
- The specific protein composition of amyloid fibrils can vary, influencing disease characteristics.
Purpose of the Study:
- To determine the complete amino acid sequence of the glycosylated amyloid protein AL MS.
- To investigate the structural and homological characteristics of AL MS.
Main Methods:
- Purification of AL MS from spleen amyloid fibrils using gel filtration.
- Protein characterization via SDS-PAGE, amino acid analysis, and Edman degradation.
- Enzymatic digestion (tryptic, V8 protease, chymotrypsin, pyroglutamate aminopeptidase) and chemical cleavage (BNPS-skatole) to establish the sequence.
Main Results:
- The complete amino acid sequence of 168 residues for AL MS was established.
- AL MS showed glycosylated protein bands (22-32 kDa) indicating N-terminal fragment polymerization.
- Homology was found with immunoglobulin light chain variable subgroup lamda I, with unique substitutions at Gly(57) and Arg(61).
Conclusions:
- The determined sequence provides insight into the molecular basis of AL MS amyloidosis.
- Unique amino acid substitutions in AL MS may affect its three-dimensional structure and amyloidogenic properties.