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Localization of Two Additional Hypervariable Regions in Immunoglobulin Heavy Chains
J. Michael Kehoe and J. Donald Capra
Proceedings of the National Academy of Sciences of the United States of America
Vol. 68, No. 9 (Sep., 1971), pp. 2019-2021
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/60840
Page Count: 3
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Cyanogen bromide fragments were isolated from the heavy chains of three human IgG myeloma proteins of the VHIII subgroup, sequenced by an automated method, and localized to the variable region. Inspection of these sequences, together with corresponding stretches from both human and animal proteins (studied in other laboratories) led to the detection of two additional hypervariable regions characteristic of the VH segment of immunoglobulin heavy chains. These areas of hypervariability, involving heavy-chain residues 86-91 and 101-109, were separated by a region of relative constancy. The close relationship of these two hypervariable regions, and the previously described first heavy-chain hypervariable region (residues 31-37), to the first heavy-chain disulphide bridge implies that the three hypervariable areas might be in close steric approximation in native immunoglobulin molecules. Examination of the sequences of the terminal portion of VH of all these proteins (the segment from residue 95 to the beginning of homology region CH1)) revealed that no subgroup-specific residues could be identified in this area. Thus, heavy-chain subgroup distinctions may not extend through the entire variable region.
Proceedings of the National Academy of Sciences of the United States of America © 1971 National Academy of Sciences