Mitochondrial ATP synthase complex: interaction of its F/sub 1/ adenosinetriphosphatase moiety with the heavy atom iodine

Journal Article · Tue Jun 30 00:00:00 EDT 1987 · Biochemistry; (United States)

OSTI ID:5994623

Petrone, G; Garboczi, D N; Pedersen, P L

Studies were carried out to determine whether a simple electron-dense heavy atom like iodine could be introduced selectively into one or more of the subunits of the mitochondrial ATP synthase complex of rat liver. Surprisingly, very low amounts of iodine are incorporated into the isolated F/sub 1/ moiety of this complex under conditions which result in a marked loss of catalytic activity. ATPase activity is inactivated in a concentration-dependent manner at pH 7.5 with half-maximal inactivation occurring at about 40 ..mu..M iodine. A maximum of only 10 atoms of iodine are incorporated per F/sub 1/ molecule under conditions where inhibition of ATPase activity is linearly related to iodine incorporation. The molecular size of F/sub 1/ after iodination is unchanged, indicating that inactivation is due to modification of essential amino acid residues rather than subunit dissociation. Treatment of F/sub 1/ with 20-50 ..mu..M (/sup 125/I)iodine followed sequentially by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography showed that the ..beta.. subunit is preferentially labeled. Significantly, about two atoms of iodine per ..beta.. subunit are incorporated. Nucleotide binding to F/sub 1/ is unaltered by iodine, and neither phosphate, MgADP, nor MgATP protects F/sub 1/ against inhibition by this agent. Rather, loss of ATPase activity upon iodination appears to be associated with one or more pH-sensitive groups. These studies represent the first attempt to introduce a heavy atom into an F/sub 1/-ATPase preparation in a selective manner. The results show that at low concentrations iodine does react preferentially with ..beta.. subunits of the rat liver enzyme while inactivating the catalytic capacity of the intact complex. These findings may prove useful in future studies directed at understanding structural-functional relationships within ATP synthase complexes.

• Research Organization: Johns Hopkins Univ., Baltimore, MD
• OSTI ID: 5994623
• Journal Information: Biochemistry; (United States), Vol. 26:13
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ATP-ASE
AUTORADIOGRAPHY
STRUCTURE-ACTIVITY RELATIONSHIPS
IODINE 125
UPTAKE
ELECTROPHORESIS
ENZYME ACTIVITY
INACTIVATION
LABELLED COMPOUNDS
LIVER
MITOCHONDRIA
RATS
ACID ANHYDRASES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
GLANDS
HYDROLASES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
MAMMALS
NUCLEI
ODD-EVEN NUCLEI
ORGANOIDS
ORGANS
PHOSPHOHYDROLASES
RADIOISOTOPES
RODENTS
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics