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Acta Crystallogr D Struct Biol. 2017 Jul 1;73(Pt 7):609-617. doi: 10.1107/S2059798317007677. Epub 2017 Jun 28.

Seeing but not believing: the structure of glycerol dehydrogenase initially assumed to be the structure of a survival protein from Salmonella typhimurium.

Author information

1
Molecular Biophysics Unit, Indian Institute of Science, Bengaluru, Karnataka 560 012, India.

Abstract

The determination of the crystal structure of a mutant protein using phases based on a previously determined crystal structure of the wild-type protein is often a straightforward molecular-replacement protocol. Such a structure determination may be difficult if there are large-scale structural differences between the wild-type and mutant proteins. In this manuscript, an interesting case is presented of the unintentional crystallization of a contaminant protein which shared some structural features with the presumed target protein, leading to difficulties in obtaining a completely satisfactory molecular-replacement structure solution. It was not immediately evident that the initial structure solution was incorrect owing to the poor quality of the X-ray diffraction data and low resolution. The structure was subsequently determined by improving the quality of the data and following a sequence-independent MarathonMR protocol. The structure corresponded to that of glycerol dehydrogenase, which crystallized as a contaminant, instead of the presumed mutant of a survival protein encoded by Salmonella typhimurium. The reasons why a solution that appeared to be reasonable was obtained with an incorrect protein model are discussed. The results presented here show that a degree of caution is warranted when handling large-scale structure-determination projects.

KEYWORDS:

MarathonMR; contaminant; glycerol dehydrogenase; molecular replacement; serendipity

PMID:
28695861
DOI:
10.1107/S2059798317007677
[Indexed for MEDLINE]

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