ATP modulation of the electron transfer between cytochrome c and cytochrome c oxidase

Citation

Lin, Jian (1995) ATP modulation of the electron transfer between cytochrome c and cytochrome c oxidase. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/k5cg-8r54. https://resolver.caltech.edu/CaltechETD:etd-10182007-085924

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The mechanism by which ATP modulates the electron transfer activity of cytochrome [...] and cytochrome [...] oxidase (CcO) has been extensively investigated by the present thesis. The subunit location of magnesium ion of CcO has been identified as the subunit IV by chemical modification and amino acid sequence analysis. The pathway for the first electron input from cytochrome [...] to CcO has been studied by laser flash photolysis with native, type I, type II, [...]-depleted CcO. The first electron from cytochrome [...] inputs directly to either heme [...] or [...] with different rate. The electron input to [...] was finally deposited to heme [...] via fast electron transfer from [...] to heme [...]. The effect of 8-azido-ATP-modification on cytochrome [...] activity was examined by transient electron transfer, steady-state, and binding studies. The 8-azido-ATP-modification does significantly decrease the rate of electron transfer from heme [...] to heme [...], of CcO. The retardation effect of the 8-azido-ATP-modification on cytochrome [...] is largely due to the disruption of the cytochrome [...] docking surface for CcO, which results in different docking conformation assumed by modified cytochrome [...] to CcO. On the other hand, the effect of ATP binding to CcO on the electron input from cytochrome [...] to heme [...] has been extensively assayed by transient absorption experiments. 8-azido-ATP-modification of CcO has been shown to have similar effect on steady-state kinetics, binding affinity for cytochrome [...] and first electron input rate from cytochrome [...] as ATP non-covalent binding. The 8-azido-ATP-modification or ATP non-covalent binding to CcO decreases the electron transfer rate from cytochrome [...] to heme [...] to about 60% of that of native enzyme by the perturbation of the cytochrome [...] binding on CcO, which leads to a change of electronic coupling and/or branching of the electron input from cytochrome [...] to [...] (or heme [...]). The binding of ATP to CcO have been probed by ATP analog, TNP-ATP. The binding of TNP-ATP to CcO have been shown to have higher affinity than ATP itself. The higher binding affinity of TNP-ATP to CcO is due to a binding energy contributed by the interaction of TNP group with detergent. This high affinity TNP-ATP binding is relevant to the ATP effect as shown by steady-state kinetics, and binding studies. The ATP binding site at subunit IV of CcO is, thus, very close to lipid bilayer. The magnesium ion, located in subunit IV, is likely to provide the binding site for the ATP binding to CcO.

Thesis Files