(499.7) Visualizing the Gas Channel of a Monofunctional Carbon Monoxide Dehydrogenase

Poster Board Number: A209

Alison Biester (Massachusetts Institute of Technology ), Sébastien Dementin (Centre National de la Recherche Scientifique), Catherine Drennan (Massachusetts Institute of Technology, Howard Hughes Medical Institute, Canadian Institute for Advanced Research)

Carbon monoxide dehydrogenase (CODH) plays an important role in the processing of one-carbon gases carbon monoxide and carbon dioxide. In CODH enzymes, these gases are channeled to and from the Ni-Fe-S active sites using hydrophobic cavities.  In this work, we investigate these gas channels in a monofunctional CODH from Desulfovibrio vulgaris, which is unusual among CODHs for its oxygen-tolerance. Based on computational predictions, we expect that monofunctional D. vulgaris CODH will have gas channels different from those of bifunctional Moorella thermoacetica carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS). By pressurizing D. vulgaris CODH protein crystals with xenon and solving the structure to 2.04 Å resolution, we identify 12 xenon sites per CODH monomer, thereby elucidating hydrophobic channels used for CO transport. We find that D. vulgaris CODH has one CO channel that has not been experimentally validated previously in a CODH, and a second channel that is shared with Moorella thermoacetica carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS). This experimental visualization of D. vulgaris CODH gas channels lays groundwork for further exploration of factors contributing to oxygen-tolerance in this CODH, as well as study of channels in other CODHs.

Support or Funding Information

The authors thank Elizabeth Wittenborn, Rebekah Bjork, and Lindsey Backman (MIT) for valuable conversations. We additionally thank Douglas C. Rees and the Stanford Synchrotron Radiation Laboratory (SSRL) for conceptualization of the xenon pressure cell design. This work was supported by National Institutes of Health Grants R35 GM126982 (to CLD) and funded by the Centre National de la Recherche Scientifique, Aix Marseille University and the French Agence Nationale de la Recherche (ANR-15-CE05-0020 and ANR-17-CE11-0027). CLD is a Howard Hughes Medical Institute Investigator and a fellow of the Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research. SD is a part of FrenchBIC. This work is based on research conducted at the Advanced Photon Source on the Northeastern Collaborative Access Team beamlines, which are funded by the National Institute of General Medical Sciences from the NIH (P41 GM103403). The Eiger2 16M detector on beamline 24-ID-C is funded by a NIH Office of Research Infrastructure Programs High End Instrumentation grant (S10 RR029205). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This work is also based on research conducted at the Stanford Synchrotron Radiation Laboratory (SSRL). SSRL, a national user facility, is operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program, and the National Institute of General Medical Sciences.