An essential intermediate in the folding of dihydrofolate reductase |
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Authors: | Heidary D K O'Neill J C Roy M Jennings P A |
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Affiliation: | Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0359, USA. |
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Abstract: | The folding of Escherichia coli dihydrofolate reductase was examined at pH 7.8 and 15 degrees C by using stopped-flow fluorescence and absorbance spectroscopies. The formation of a highly fluorescent intermediate occurs with relaxation times ranging between 142 and 343 msec, whereas stopped-flow absorbance spectroscopy using methotrexate binding assays shows a distinct lag phase during these time frames for the native state. The lag in absorbance kinetics and the lack of fast-track folding events indicate that the formation of this ensemble of intermediates is an obligatory step in the folding reaction. |
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