Faculty

Richter Research Synopsis:

ATP synthase Structure and Function

The F₁F_O-ATP synthase is a tiny molecular rotary motor driven by binding and hydrolysis of ATP in one direction and by trans-membrane proton flux in the other direction. This complex multi-subunit protein generates sufficient torque to propel large (1-2 micrometers) actin filaments through solution with a remarkably high energy conversion efficiency. The photosynthetic ATP synthase of higher plants has several unique properties that separate it from its mitochondrial and bacterial counterparts and that offer unique inroads to examine the mechanism of energy coupling. One such property is the presence of a special regulatory domain in the γ subunit of higher plant species which, via the reversible oxidation/reduction of an intrinsic dithiol that governs an interaction with the inhibitory ε subunit, provides a molecular "switch" mechanism that tightly controls the catalytic activity of the enzyme. The principle goal of the proposed research is to identify the productive binding interactions between the γ and ε subunits, and between these two subunits and the other F₁ subunits, that are involved in the molecular "switch" mechanism. The information to be gained from this work is likely to prove seminal in understanding natural processes that have evolved to gate the motor, in identifying the mechanism of elastic coupling between the F_O and F₁ segments, and in designing gated nanodevices for future industrial and biomedical applications. Ongoing projects involve: protein engineering, folding and ATPase complex assembly; NMR and crystallization studies of subunit structure; single molecule enzyme analysis using atomic force microscopy, fluorescence and dark-field microscopy; and surface patterning for on-chip fabrication of nanodevices to address industrial and biomedical needs.

Other projects

1) Examination of ecto-enzyme complexes associated with the plasma membranes of endothelial and cancer cells; 2) Fluorescence nucleotide and protein-protein binding studies of mammalian G proteins and adenylyl cyclase; 3) Targeting the Hsp90 multichaperone complex for cancer therapy; and 4) Targeting novel cathepsin D-like proteases as therapeutic targets for Leishmanias, tropical diseases caused by Trypanosome parasites.

Representative Publications

• Tucker, W.C., Schwarz, A., Levine, T., Du, Z., Gromet-Elhanan, Z., Richter, M.L. and Haran, G. (2004) Observation of calcium-dependent unidirectional rotational motion in recombinant photosynthetic F₁-ATPase molecules. J.Biol.Chem. 279, 47415–47418.
• Haslam, G., Richter, M.L., Wyatt, D., Ye, Q-Z. and Kitos, P.A. (2004) Estimating the number of viable animal cells in multi-well culture - a tetrazolium-based assay. Analytical Biochemistry 336, 187–195.
• Richter, M.L., Samra, H., He, F.,Giessel, A. and Kuczera, K. (2005) Coupling proton movement to ATP synthesis in the chloroplast ATP synthase Bioenergetics and Biomembranes, 37, 467–473.
• Samra, H.S., Gao, F., He, F., Hoang, E., Chen, Z., Gegenheimer, P.A., Berrie C.L. and Richter, M.L. (2006) Structural analysis of the regulatory dithiol containing domain of the chloroplast ATP synthase gamma subunit J.Biol.Chem. 281, 31041–31049.
• Quillen, E.E., Haslam, G.C., Amani-Taleshi, D., Knight, J.A. Samra, H.S., Wyatt, D.E., Richter, M.L. and Kitos, P.A. (2006) Ecto-adenylate kinase and plasma membrane ATP synthase activities of human vascular endothelial cells J.Biol.Chem. 281, 20728–20737.
• Mou, T-C., Gille, A., Suryanarayana, S., Richter, M.L., Seifert, R. and Sprang, S.R. (2006) Structural basis for inhibitor selectivity targeting to mammalian adenylyl cyclase Molecular Pharmacology 70, 878–886.
• He, F., Samra, H.S., Tucker, W.C., Mayans, D.R., Huang, E., Gromet-Elhanan, Z., Berrie, C.L. and Richter, M.L. (2007) Mutations within the C-terminus of the gamma subunit of the photosynthetic F1-ATPase activate MgATP hydrolysis and attenuate the stimulatory oxyanion effect Biochemistry 46, 2411–2418.
• He, F., Samra, H.S., Johnson, E.A., Degner, N.R., McCarty, R.E. and Richter, M.L. (2008) C-terminal mutations in the chloroplast ATP synthase gamma subunit impair ATP synthesis and stimulate ATP hydrolysis Biochemistry, 47, 836–844.
• Samra, H.S., He, F., Degner, N.R., and Richter, M.L. (2008, in press) The role of specific b-g subunit interactions in oxyanion stimulation of the MgATP hydrolysis of a hybrid photosynthetic F1-ATPase Bioenergetics & Biomembranes.

Search PubMed for articles by Mark Richter.