Protein Conformation and Disease:  Pathological Consequences of Analogous Mutations in Homologous Proteins

• Published in: Biochemistry (Easton) Vol. 39; no. 50; pp. 15291 - 15296
• Main Authors: Stevens, Fred J, Pokkuluri, Phani R, Schiffer, M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19-12-2000
• Subjects: Amino Acid Sequence; Animals; Disease Susceptibility; Genes, Immunoglobulin; Humans; Immunoglobulins - chemistry; Immunoglobulins - genetics; Molecular Sequence Data; Mutation; Protein Conformation; Sequence Homology; Structure-Activity Relationship
• DOI: 10.1021/bi001017x
• EISSN: 1520-4995
• ISSN: 0006-2960

The antibody light chain variable domain (VL)1 and myelin protein zero (MPZ) are representatives of the functionally diverse immunoglobulin superfamily. The VL is a subunit of the antigen-binding component of antibodies, while MPZ is the major membrane-linked constituent of the myelin sheaths that coat peripheral nerves. Despite limited amino acid sequence homology, the conformations of the core structures of the two proteins are largely superimposable. Amino acid variations in VL account for various conformational disease outcomes, including amyloidosis. However, the specific amino acid changes in VL that are responsible for disease have been obscured by multiple concurrent primary structure alterations. Recently, certain demyelination disorders have been linked to point mutations and single amino acid polymorphisms in MPZ. We demonstrate here that some pathogenic variations in MPZ correspond to changes suspected of determining amyloidosis in VL. This unanticipated observation suggests that studies of the biophysical origin of conformational disease in one member of a superfamily of homologous proteins may have implications throughout the superfamily. In some cases, findings may account for overt disease; in other cases, due to the natural repertoire of inherited polymorphisms, variations in a representative protein may predict subclinical impairment of homologous proteins.