sup 31 P NMR saturation-transfer study of the in situ kinetics of the mitochondrial adenine nucleotide translocase

Journal Article · Tue Aug 27 00:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00098a011· OSTI ID:5821349

Masiakos, P T; Williams, G D; Berkich, D A; Smith, M B; LaNoue, K F ^[1]

---

1. Pennsylvania State Univ., Hershey (United States)

The exchange of intramitochondrial ATP (ATP{sub in}) for extramitochondrial ATP (ATP{sub out}) was measured by using {sup 31}P NMR spectroscopy over a range of temperatures in isolated rat liver mitochondria oxidizing glutamate and succinate in the presence of external ATP but no added ADP (state 4). The rate of this exchange is more than an order of magnitude faster than rates reported previously that were determined by using isotopic techniques in the presence of oligomycin, the potent ATPase inhibitor. Differences are ascribed in part to the low levels of matrix ATP present in oligomycin-treated mitochondrial. Intramitochondrial ATP content regulates the rate of the ATP{sub in}/ATP{sub out} exchange. At 18C, the concentration of internal ATP that produces half-maximal transport rate is 6.6{plus minus}0.12 nmol/mg of mitochondrial protein. The relationship between substrate concentration and flux is sigmoidal and is 90% saturated at 11.3{plus minus}0.18 nmol/mg of mitochondrial protein. Since the measured rates of exchange of ATP{sub in} for ATP{sub out} are almost 10 times faster than the ATP synthase (ATP/P{sub i}) exchange rates, the translocase cannot limit net ATP/P{sub i} exchange in state 4. It may, nonetheless, limit net synthesis of ATP under other conditions when matrix ATP concentration is lower than in state 4 and when external ADP is present at higher concentrations than in these experiments.

• OSTI ID: 5821349
• Journal Information: Biochemistry; (United States), Vol. 30:34; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ATP
MEMBRANE TRANSPORT
MITOCHONDRIA
BIOCHEMICAL REACTION KINETICS
TRANSFERASES
NUCLEAR MAGNETIC RESONANCE
ADENINES
ENZYME INHIBITORS
PHOSPHORUS 31
AMINES
ANTIMETABOLITES
AROMATICS
AZAARENES
CELL CONSTITUENTS
DRUGS
ENZYMES
HETEROCYCLIC COMPOUNDS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHORUS ISOTOPES
PROTEINS
PURINES
REACTION KINETICS
RESONANCE
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques