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A new extra sequence at the amino terminal of a mu heavy chain disease protein (DAG)
C Mihaesco1, P Ferrara, J C Guillemot
1Laboratoire d'Immunochimie et d'Immunopathologie, U.108 INSERM, Hôpital Saint-Louis, Paris, France.
Abstract:
The primary structure of a human mu heavy chain (DAG) protein is described. The native protein is a circular decamer with a molecular weight (Mr) of 500 kDa, each decamer being constituted of the constant domains C mu 2, C mu 3 and C mu4 and interlinked by 15 disulfide bridges. At its NH2-terminal each monomeric chain starts with an "extra sequence". The amino acid sequence of this segment is Arg-Gln-Ser-Asp-Asp-Pro-Val-Leu-Arg-Gly-Thr-Thr-Val-Pro-Val-Thr-Glu and its reinitiation point is located at Val223 (Gal numbering), at the beginning of C mu 2. This sequence has no homology with any other protein included in the present databases.
Insights
This study details the primary structure of the human mu heavy chain (DAG) protein, a circular decamer. Its unique N-terminal extra sequence shows no homology to known proteins.
Area of Science:
- Immunology
- Protein Chemistry
- Molecular Biology
Background:
- The human mu heavy chain (DAG) protein is a key component in immune responses.
- Understanding its primary structure is crucial for elucidating its function and interactions.
Purpose of the Study:
- To describe the primary structure of the human mu heavy chain (DAG) protein.
- To characterize its oligomeric state, molecular weight, and constituent domains.
- To identify and analyze the N-terminal extra sequence.
Main Methods:
- Primary structure analysis of the human mu heavy chain (DAG) protein.
- Determination of oligomeric state and molecular weight.
- Sequence homology searches against protein databases.
Main Results:
- The human mu heavy chain (DAG) protein exists as a circular decamer (500 kDa).
- Each monomer comprises constant domains C mu 2, C mu 3, and C mu4, linked by 15 disulfide bridges.
- An N-terminal extra sequence (Arg-Gln-Ser-Asp-Asp-Pro-Val-Leu-Arg-Gly-Thr-Thr-Val-Pro-Val-Thr-Glu) was identified, initiating at Val223.
- This extra sequence exhibits no homology with existing protein databases.
Conclusions:
- The human mu heavy chain (DAG) protein possesses a unique N-terminal sequence with no known homologs.
- The described primary structure provides a foundation for further functional and structural studies of this protein.