Format

Send to

Choose Destination
See comment in PubMed Commons below
Structure. 2014 Jun 10;22(6):899-910. doi: 10.1016/j.str.2014.04.016. Epub 2014 May 29.

Crystal cryocooling distorts conformational heterogeneity in a model Michaelis complex of DHFR.

Author information

1
Department of Bioengineering and Therapeutic Sciences and California Institute for Quantitative Biology, University of California, San Francisco, San Francisco, CA 94158, USA.
2
Joint Center for Structural Genomics, Stanford Synchrotron Radiation Lightsource, Stanford, CA 94025, USA.
3
Center for Systems and Synthetic Biology, University of California, San Francisco, San Francisco, CA 94158, USA.
4
Department of Biochemistry and Chemistry, Brandeis University, Waltham, MA 02454, USA; Department of Neurology and Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02139, USA.
5
Department of Neurology and Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02139, USA.
6
Department of Biochemistry and the Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA. Electronic address: mwilson13@unl.edu.
7
Department of Bioengineering and Therapeutic Sciences and California Institute for Quantitative Biology, University of California, San Francisco, San Francisco, CA 94158, USA. Electronic address: james.fraser@ucsf.edu.

Abstract

Most macromolecular X-ray structures are determined from cryocooled crystals, but it is unclear whether cryocooling distorts functionally relevant flexibility. Here we compare independently acquired pairs of high-resolution data sets of a model Michaelis complex of dihydrofolate reductase (DHFR), collected by separate groups at both room and cryogenic temperatures. These data sets allow us to isolate the differences between experimental procedures and between temperatures. Our analyses of multiconformer models and time-averaged ensembles suggest that cryocooling suppresses and otherwise modifies side-chain and main-chain conformational heterogeneity, quenching dynamic contact networks. Despite some idiosyncratic differences, most changes from room temperature to cryogenic temperature are conserved and likely reflect temperature-dependent solvent remodeling. Both cryogenic data sets point to additional conformations not evident in the corresponding room temperature data sets, suggesting that cryocooling does not merely trap preexisting conformational heterogeneity. Our results demonstrate that crystal cryocooling consistently distorts the energy landscape of DHFR, a paragon for understanding functional protein dynamics.

PMID:
24882744
PMCID:
PMC4082491
DOI:
10.1016/j.str.2014.04.016
[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science Icon for PubMed Central
    Loading ...
    Support Center