Binuclear transition-metal complexes as new reagents for selective cross-linking of proteins. Coordination of cytochrome c to dirhodium(II). mu. -tetraacetate
- Iowa State Univ., Ames (USA)
This study introduces binuclear transition-metal complexes as reagents for selective covalent cross-linking of proteins. Incubation of horse cytochrome c (designated cyt) with Rh{sub 2}(OAc){sub 4} under mild conditions yields the diprotein complex, Rh{sub 2}(OAc){sub 4}(cyt){sub 2}, whose composition is established by size-exclusion chromatography, uv-vis spectroscopy, and {sup 1}H NMR spectroscopy. The protein molecules are coordinated to the Rh atoms via the imidazole (Im) rings of their His 33 residues, as shown by uv difference and {sup 1}H NMR spectroscopy, by the pH effect on the complex formation, and by the control experiments with tuna cytochrome c. The diprotein complex is stable under ordinary conditions, and yet it can be cleaved, and the native protein recovered, by treatment with a suitable strong nucleophile. Spectroscopic and electrochemical measurements show that the structural and redox properties of cytochrome c are not perturbed significantly by cross-linking. Comparison between Rh{sub 2}(OAc){sub 4}(Im){sub 2} and Rh{sub 2}(OAc){sub 4}(cyt){sub 2} shows that the complex containing small ligands is not an entirely realistic model of the complex containing proteins. In particular, the enhanced stability of the latter toward hydrolysis may be due to steric bulk of the protein ligands and to hydrogen bonds that amino acid side chains may form with the inorganic link. Some of the findings of this study may pertain to the mechanism of antitumor action of the Rh{sub 2}(RCOO){sub 4} complexes. 86 refs., 2 tabs.
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5719346
- Journal Information:
- Inorganic Chemistry; (USA), Vol. 27:15; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CYTOCHROMES
CHEMICAL BONDS
RHODIUM COMPOUNDS
EXPERIMENTAL DATA
NMR SPECTRA
PROTONS
BARYONS
DATA
ELEMENTARY PARTICLES
FERMIONS
HADRONS
INFORMATION
NUCLEONS
NUMERICAL DATA
ORGANIC COMPOUNDS
PIGMENTS
PROTEINS
REFRACTORY METAL COMPOUNDS
SPECTRA
TRANSITION ELEMENT COMPOUNDS
550200* - Biochemistry
400201 - Chemical & Physicochemical Properties