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The amino acid sequence of a carbohydrate-containing immunoglobulin-light-chain-type amyloid-fibril protein
Abstract:
The amino acid sequence of an amyloid-fibril protein Es492 of immunoglobulin-lambda-light-chain origin (AL) was elucidated. The amyloid fibrils were obtained from the spleen of a patient who died from systemic amyloidosis. The amino acid sequence was elucidated from structural studies of peptides derived from digestion of the protein with trypsin, thermolysin, chymotrypsin and Staphylococcus aureus V8 proteinase and from cleavage of the protein with CNBr and BNPS-skatole. A heterogeneity in the length of the polypeptide was seen in the C-terminal region. The protein was by sequence homology to other lambda-chains shown to be of the V lambda II subgroup. Although an extensive homology was seen, some amino acid residues in positions 26, 31, 32, 40, 44, 93, 97, 98 and 99 have not previously been reported in these positions of V lambda II proteins. The significance of these residues in the fibril formation is unclear. The protein was found to contain carbohydrate, with glycosylation sites in two of the hypervariable regions.
Insights
Researchers elucidated the amino acid sequence of an amyloid-fibril protein (AL) from a patient with systemic amyloidosis. This protein belongs to the V lambda II subgroup, with unique residues potentially influencing fibril formation.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Systemic amyloidosis is characterized by the deposition of amyloid fibrils in various organs.
- Amyloid-fibril proteins, such as immunoglobulin light chains, are implicated in disease pathogenesis.
- Understanding the specific protein sequence and structure is crucial for elucidating disease mechanisms.
Purpose of the Study:
- To determine the complete amino acid sequence of the amyloid-fibril protein Es492.
- To identify the specific subgroup of immunoglobulin lambda light chain origin.
- To investigate potential structural variations and their implications in amyloid formation.
Main Methods:
- Proteolytic digestion of amyloid fibrils with trypsin, thermolysin, chymotrypsin, and Staphylococcus aureus V8 proteinase.
- Chemical cleavage of the protein using CNBr and BNPS-skatole.
- Amino acid sequencing of resulting peptides using established structural studies.
- Sequence homology analysis to classify the protein within immunoglobulin lambda light chain subgroups.
Main Results:
- The amino acid sequence of the amyloid-fibril protein Es492 was elucidated.
- The protein was identified as belonging to the V lambda II subgroup of immunoglobulin lambda light chains.
- Heterogeneity in polypeptide length was observed at the C-terminal region.
- Several unique amino acid residues were identified in specific positions compared to known V lambda II proteins.
- The presence of glycosylation sites in two hypervariable regions was confirmed.
Conclusions:
- The elucidated sequence provides critical data for understanding AL amyloidosis.
- The identified unique residues may play a role in amyloid fibril formation, though their significance requires further investigation.
- The glycosylation of the protein could influence its stability and aggregation properties.