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Complete Amino acid Sequence of a Mouse Immunoglobulin α Chain (MOPC 511)

Elizabeth A. Robinson and Ettore Appella
Proceedings of the National Academy of Sciences of the United States of America
Vol. 77, No. 8, [Part 2: Biological Sciences] (Aug., 1980), pp. 4909-4913
Stable URL: http://www.jstor.org/stable/9218
Page Count: 5
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Complete Amino acid Sequence of a Mouse Immunoglobulin α  Chain (MOPC 511)
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Abstract

The complete amino acid sequence of the 432-residue heavy (α) chain of mouse myeloma MOPC 511 has been determined. The variable region of the α chain of IgA 511, a phosphocholine-binding protein, is highly homologous to that of the other phosphocholine-binding immunoglobulins. Comparison of the 511 α chain constant region with that of other mouse and human heavy chains shows that sequence divergences and deletions are more extensive within domain disulfide bridges than in other parts of a domain. The CH3 domain disulfide bridge of the 511 α chain, for example, consists of only 28 amino acid residues compared to 60 residues for other chains and domains. Sequence divergences are also apparent at the CH2/CH3 domain boundary, an area where a number of frameshift mutations have occurred. One mutant, mouse IgA 47A, lacks the entire CH3 domain. Comparison of the 511 α chain with the 47A α chain reveals two nonconservative amino acid changes at the COOH terminus of the 47A chain, Ser-Gln for Val-Thr in the 511 chain. These changes and the deletion of the CH3 domain can be explained by a single genetic event--namely, a frameshift mutation followed by premature chain termination. The remainder of the 47A constant region, including the hinge region, is identical to the 511 α chain, except for two conservative changes in the CH1 domain: serine-126 and threonine-197 in the 511 α chain are both replaced by alanine in the 47A chain.

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