This project has been concerned with study of the composition, structure, mechanism of action and interaction of mitochondrial enzyme complexes I (NADH:ubiquinone, Q, oxidoreductase), II (succinate: Q oxidoreductase), III (ubiquinol: cytochrome c oxidoreductase), and V (ATP synthase). The studies proposed here include the following: Complex I - (a) Continuation of the use of controlled and differential proteolysis to identify the electron paramagnetic resonance-visible iron-sulfur clusters associated with the 75 and the 23 kDa subunits, and their involvement in electron transfer from NADH to Q. (b) We have discovered that bovine complex I contains 4 nicotinamide nucleotide- binding subunits not involved in electron transfer from NADH to Q. These are subunits 42 kDa, NAD(H)-specific; 39 kDa, NADP(H)-specific; 30 kDa, NAD(H)/NADP(H)-binding; and 18-20 kDa, NADP(H)-specific. The possible role of these subunits together with the acyl carrier protein of complex I in de novo intramitochondrial fatty acid synthesis will be investigated. Complex III - Continuation of the study of the mechanism of electron transfer by complex III, using Rhodobacter capsulatus chromatophores containing mutations in the heme bL domain of cytochrome b or in the extrinsic domain of the iron-sulfur protein (ISP). These studies are important, because (a) our results with the bovine system have indicated that Q is not necessary for electron transfer between bL and ISP, (b) complex III x-ray diffraction results of two groups do not show Q in this region, and (c) the extrinsic domain of ISP appears to swing between cytochromes b and c1. Complex V - (a) Study of the involvement of subunits b, d, e, f g, and A6L as possible membrane-bound anchors for the ATPase inhibitor protein and factor B. (b) Study of the possible involvement of subunits F6, d, e, f g and A6L together with subunits b and OSCP as components of the stator of the bovine mitochondrial ATP synthase. Mitochondrial defects cause a variety of debilitating human neuromuscular degenerative diseases, whose prevention and treatment require a knowledge of the structure and function of mitochondria at the molecular level.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK008126-38
Application #
6380344
Study Section
Physical Biochemistry Study Section (PB)
Program Officer
Sechi, Salvatore
Project Start
1977-04-15
Project End
2002-03-31
Budget Start
2001-04-01
Budget End
2002-03-31
Support Year
38
Fiscal Year
2001
Total Cost
$597,377
Indirect Cost
Name
Scripps Research Institute
Department
Type
DUNS #
781613492
City
La Jolla
State
CA
Country
United States
Zip Code
92037