Robert K. Nakamoto
Primary AppointmentProfessor, Molecular Physiology and Biological Physics
- PhD, University of Maryland
- AB, Zoology, University of California, Berkeley, CA
- PhD, Biochemistry, University of Maryland, Baltimore, MD
- Postdoc, Biochemistry, Stanford University, Stanford, CA
- Postdoc, Biochemistry and Genetics, Yale University, New Haven, CT
Structure-Function of Active Transporters
All organisms carefully control the concentration of solutes within their cells, and are able to import required compounds or exclude cytotoxic ones. The protein machines that carry out these tasks are the primary active transporters, or pumps. These large, and often multiple subunit, integral membrane proteins utilize chemical energy usually from the hydrolysis of adenosine triphosphate or ATP, or the electrochemical energy stored in other ion gradients, to translocate solutes across a membrane against concentration gradients. Our laboratory concentrates on three such transporters: the P-glycoprotein, a pump that has the ability to transport a broad range of compounds and confers multiple drug resistance to tumor cells; the ubiquitous FOF1 ATP synthase which uses the energy of an electrochemical gradient of protons to generate the vast majority of ATP; and the vitamin B12 transporter, BtuB of gram negative bacteria, which moves cyano-cobalamin across the outer membrane by a mechanism that is dependent upon the electrochemical gradient of protons across the inner cytoplasmic membrane.
Our goal is to understand the molecular mechanisms of these different transporters. We use a variety of biochemical, biophysical and structural approaches combined with genetic and molecular biological approaches to probe the structure-function relationships. In such ways, we can obtain measurements of the structural dynamics that occur during the transport cycle. The dynamics are correlated to the kinetics of the partial reactions occurring during transport and the energetics of these transitions. The data are used to generate models which can then be computationally simulated.