Structural features, cytochrome

As another example, the three-dimensional structure of Cytochrome c has been determined on the basis of structural information from pseudocontact paramagnetic chemical shifts, Curie-Dipolar cross-correlation, secondary structure constraints, dipolar couplings and 15N relaxation data [103]. This protein has a paramagnetic center, and therefore the above-mentioned conformational restraints can be derived from this feature. Dipolar couplings do not average to zero because of the susceptibility tensor anisotropy of the protein. The structure determination of this protein without NOE data gives an RMSD (root... 

We are at the discovery stage for determining the ability of various bacteria to reduce metals and nonessential compounds. Mechanisms for these reductions generally have not yet been established, and it is apparent that much is unknown. A number of questions pertaining to reduction are raised Which elements and compounds are reduced at the cell surface Why are some of the compounds not reduced at the cell surface but become reduced at the plasma membrane or in the cytoplasm What is the nature of the nonenergetic reactions in the cytoplasm of the bacterial cell What are the physiologic substrates for the cytochromes and which reactions occur because of substitution of chemicals due to similar structural features ... 

Important Structural Features of the Active Sites of Metal Centres Deoxyhemoglobin, Cytochrome c, Vitamin Bi2 ... 

The Cytochrome c/cytochrome b5 Complex Structural Features. One important feature of the c/b5 system is the detailed structural information which is available for these proteins. The structure of cytc is nown at 1.5A resolution in both the oxidized and reduced states. EXAFS studies have also been reported, which show no observable changes i getal coordination geometry on oxidation/reduction. The cytochrome b5 s ucture has also been solved at high resolution by Matthews et al. 

It has long been established that the functional unit of cytochrome oxidase contains four redox-active metal centres. Two of these, cytochromes a and a3, contain heme A (Fig. 5-23) coordinated in different ways in subunit I. The heme group is not covalently linked to the protein. The main structural features are the carbonyl group at position 8 and the isoprenoid chain at position 2 of the porphyrin ring. 

Another important and highly conserved feature in all structures of cytochromes P450 with only a few exceptions is the... 

The two-domain, structural motif in FNR represents a common structural feature in a large class of enzymes that catalyze electron transfer between a nicotinamide dinucleotide molecule and a one-electron carrier. Beside the photosynthetic electron-transfer enzyme, others non-photosynthetic ones include flavodoxin reductase, sulfite reductase, nitrate reductase, cytochrome reductase, and NADPH-cyto-chrome P450 reductase. FNR belongs to the group of so-called dehydrogenases-electron transferases, i.e., flavoproteins that catalyze electron transfer from two, one-electron donor molecules to a single two-electron acceptor molecule. 

Black, S.D. and M.J. Coon (1982). Structural features of liver microsomal NADPH-cytochrome P450 reductase hydrophobic domain, hydrophilic domain and connecting region. J. Biol. Chem. 257, 5929-5938. 

Though speculative, these suggestions are now amenable to experimental evaluation. I am suflSciently optimistic to beheve that truly significant progress will soon be made in the evaluation of structural features and reactions of the very complex enzyme cytochrome c oxidase as well as for other hemeproteins. This progress will result in no small part from the applications of independent physical methods at several levels—the hemin, the protein, and the tissue levels. 

A broad review of the pharmacokinetic basis for H2 antagonlst drug interactions Includes a discussion of structural features present in clmetldine, but not ranitidine, that contribute to binding to the cytochrome P450 linked mixed function oxidase. ... 

---