Abstract

The betagamma-crystallin superfamily consists of a class of homologous two-domain proteins with Greek-key fold. Protein S, a Ca(2+)-binding spore-coat protein from the soil bacterium Myxococcus xanthus exhibits a high degree of sequential and structural homology with gammaB-crystallin from the vertebrate eye lens. In contrast to gammaB-crystallin, which undergoes irreversible aggregation upon thermal unfolding, protein S folds reversibly and may therefore serve as a model in the investigation of the thermodynamic stability of the eye-lens crystallins. The thermal denaturation of recombinant protein S (PS) and its isolated domains was studied by differential scanning calorimetry in the absence and in the presence of Ca(2+) at varying pH. Ca(2+)-binding leads to a stabilization of PS and its domains and increases the cooperativity of their equilibrium unfolding transitions. The isolated N-terminal and C-terminal domains (NPS and CPS) obey the two-state model, independent of the pH and Ca(2+)-binding; in the case of PS, under all conditions, an equilibrium intermediate is populated. The first transition of PS may be assigned to the denaturation of the C-terminal domain and the loss of domain interactions, whereas the second one coincides with the denaturation of the isolated N-terminal domain. At pH 7.0, in the presence of Ca(2+), where PS exhibits maximal stability, the domain interactions at 20 degrees C contribute 20 kJ/mol to the overall stability of the intact protein. Study holds ProTherm entries: 6259, 6260, 6261, 6262, 6263, 6264, 6265, 6266, 6267, 6268, 6269, 6270, 6271, 6272, 6273, 6274, 6275, 6276, 6277, 6278, 6279, 6280, 6281, 6282, 6283, 6284, 6285, 6286, 6287, 6288, 6289, 6290, 6291, 6292, 6293, 6294, 6295, 6296, 6297, 6298, 6299, 6300, 6301, 6302, 6303, 6304, 6305, 6306, 6307, 6308, 6309, 6310, 6311, 6312, 6313, 6314, 6315, 6316, 6317, 6318 Extra Details: additive : EDTA(1 mM),transition 1 differential scanning calorimetry; betagamma-crystallin;,protein stability; two-domain protein; protein stability; domain interactions

Submission Details

ID: J5LfwoC24

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:31 p.m.

Version: 1

Publication Details

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