Solution conformation of bovine lens α‐and βB2‐crystallin terminal extensions

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Abstract
α‐and βB2Crystallin are the major proteins in the mammalian lens. Each of these crystallins has short, flexible terminal extensions from its domain core; the two α‐crystallin subunits have C‐terminal extensions of eight and ten amino acids whilst βB2‐crystallin has N‐ and C‐terminal extensions of 15 and 11 amino acids, respectively. The solution conformations of these chemically synthesised extensions have been examined by two‐dimensional 1H NMR spectroscopy, The N‐terminal extension of βB2‐crystallin and the C‐terminal extensions of α‐crystallin adopt little ordered structure. In the membrane‐mimicking solvent trifluoroethanol, the α‐crystallin extensions are also unstructured. In contrast, the C‐terminal extension of βB2‐crystallin in water has a structural preference towards turn‐like structures, creating a hydrophobic region involving G198, F200 and P202. In the lens, the C‐terminal extension of βB2‐crystallin is the only one of these extensions that interacts to any large extent with other crystallins. The structural preference of the C‐terminal extension of βB2‐crystallin may therefore have implications for the role of this extension in crystallin‐crystallin interactions. ©Munksgaard 1996.