Noninvasive tagging of proteins with an inorganic chromophore. Selectivity of chloro(terpyridine)platinum(II) toward amino acids, peptides, and cytochromes c
The complex (Pt(trpy)Cl)/sup +/ exhibits unexpected selectivity toward amino acid side chains in cytochromes c from Candida krusei and bakers' yeast. Although kinetic studies with amino acids and peptides as entering ligands prove this complex to be completely selective toward thiol over imidazole, His-33 and His-39 residues (in both proteins) are labeled with greater yields than the Cys-102 residue (in the bakers' yeast protein). The binding sites are determined by peptide mapping and other methods. The Pt(trpy)/sup 2+/ tags are stable, and the protein derivatives are separated by cation-exchange chromatography. The (Pt(trpy)His)/sup 2+/ and (Pt(trpy)Cys)/sup +/ chromophores are easily detected and quantitated owing to their characteristic and strong UV-vis bands. Spectroscopic and electrochemical measurements show that labeling with the new reagent does not alter the structural and redox properties of the cytochromes c. The unexpected outcome of the protein labeling indicates that, contrary to the common assumption, Cys-102 is not exposed at the protein surface. Modification of this residue with various organic reagents and dimerization of the protein must be accompanied by a perturbation of the conformation, which makes Cys-102 accessible to the reagent or to another molecule of the protein. These predictions from the labeling study are confirmed subsequently by the crystallographic study of the iso-1 cytochrome c from bakers' yeast. The inorganic complex (Pt(trpy)Cl)/sup +/ differs from the other reagents for protein modification by its noninvasiveness, a property that may well render it useful as a probe of the protein surface. 59 refs., 2 figs., 4 tabs.
- Research Organization:
- Iowa State Univ., Ames (USA)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5703355
- Journal Information:
- Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:10; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Platinum(II) complexes as spectroscopic probes for biomolecules
Effects of ancillary ligands on selectivity of protein labeling with platinum(II) chloro complexes
Related Subjects
400201 -- Chemical & Physicochemical Properties
550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AZINES
CHEMICAL REACTIONS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
DATA
ELECTROCHEMISTRY
EXPERIMENTAL DATA
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PLATINUM CHLORIDES
PLATINUM COMPOUNDS
PROTEINS
PYRIDINES
SPECTRA
TRANSITION ELEMENT COMPOUNDS