A Guide to Marxian Political Economy

Abstract

The apoenzyme of NADPH oxidoreductase, old yellow enzyme, was reconstituted with specifically 15N-labeled FMN or FMN derivs. and investigated by 15N NMR spectroscopy in the oxidized and reduced state. In the oxidized state a H bond is formed between the N(5) atom and the apoprotein. In addn., H bonds exist between the N(1) and N(3) atoms of FMN and the apoprotein. The resonance position of N(10) indicates that this atom is somewhat sp3-hybridized, i.e., lifted out of the mol. plane of the isoalloxazine ring system. In the reduced state, the N(1) atom is neg. charged and the N(3) atom forms a H bond with the apoprotein. The N(10) atom in protein-bound FMN exhibits about the same hybridization state as in free anionic reduced FMN, i.e., it is located in the plane of the isoalloxazine ring. The chem. shift of the N(5) resonance indicates that this atom is almost completely sp3-hybridized. This interpretation can also be derived from the 15N(5)-1H coupling const. Among the flavoproteins thus far studied by NMR techniques, old yellow enzyme is the only protein that shows a conformation of the reduced prosthetic group with the N(5) atom lifted out of the mol. plane. The isoelec. focusing properties of old yellow enzyme and a new easy method for the prepn. of the apoprotein are also reported. [on SciFinder (R)]