R73A and H144Q mutants of the yeast mitochondrial cyclophilin Cpr3 exhibit a low prolyl isomerase activity in both peptide and protein-folding assays |
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Authors: | Scholz C Maier P Dolinski K Heitman J Schmid F X |
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Institution: | Biochemisches Laboratorium, Universit?t Bayreuth, Germany. |
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Abstract: | Previously we reported that the R73A and H144Q variants of the yeast cyclophilin Cpr3 were virtually inactive in a protease-coupled peptide assay, but retained activity as catalysts of a proline-limited protein folding reaction Scholz, C. et al. (1997) FEBS Lett. 414, 69-73]. A reinvestigation revealed that in fact these two mutations strongly decrease the prolyl isomerase activity of Cpr3 in both the peptide and the protein-folding assay. The high folding activities found previously originated from a contamination of the recombinant Cpr3 proteins with the Escherichia coli protein SlyD, a prolyl isomerase that co-purifies with His-tagged proteins. SlyD is inactive in the peptide assay, but highly active in the protein-folding assay. |
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