A fragment of staphylococcal nuclease with an OB-fold structure shows hydrogen-exchange protection factors in the range reported for "molten globules".
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ABSTRACT:
SUBMITTER: Alexandrescu AT
PROVIDER: S-EPMC2143544 | biostudies-other | 1996 Sep
REPOSITORIES: biostudies-other
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A fragment of staphylococcal nuclease with an OB-fold structure shows hydrogen-exchange protection factors in the range reported for "molten globules".
Alexandrescu A T AT Dames S A SA Wiltscheck R R
Protein science : a publication of the Protein Society 19960901 9
Hydrogen-exchange rates for an OB-fold subdomain fragment of staphylococcal nuclease have been measured at pH 4.7 and 4 degrees C, conditions close to the minimum of acid/base catalyzed exchange. The strongest protection from solvent exchange is observed for residues from a five-stranded beta-barrel in the NMR structure of the protein. Protection factors, calculated from the experimental hydrogen-exchange rates, range between 1 and 190. Similarly small protection factors have in many cases been ...[more]
Similar Datasets
Project description:We have been interested in whether three proteins that share a five-stranded beta-barrel "OB-fold" structural motif but no detectable sequence homology fold by similar mechanisms. Here we describe native-state hydrogen exchange experiments as a function of urea for SN (staphylococcal nuclease), a protein with an OB-fold motif and additional nonconserved elements of structure. The regions of structure with the largest stability and unfolding cooperativity are contained within the conserved OB-fold portion of SN, consistent with previous results for CspA (cold shock protein A) and LysN (anticodon binding domain of lysyl tRNA synthetase). The OB-fold also has the subset of residues with the slowest unfolding rates in the three proteins, as determined by hydrogen exchange experiments in the EX1 limit. Although the protein folding hierarchy is maintained at the level of supersecondary structure, it is not evident for individual residues as might be expected if folding depended on obligatory nucleation sites. Rather, the site-specific stability profiles appear to be linked to sequence hydrophobicity and to the density of long-range contacts at each site in the three-dimensional structures of the proteins. We discuss the implications of the correlation between stability to unfolding and conservation of structure for mechanisms of protein structure evolution.
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