Amicyanin complex

It has been predicted that the His hgand flip cannot occur in amicyanin complexed with MADH because of steric hindrance due to close van der Waals contacts with residues of the neighboring small subunit of the MADH molecule (Zhu et al., 1998). 

Phe stabilizes the MADH-amicyanin complex via van der Waalsi interactions at the protein-protein interface (see Figure 5). An F97E... 

More detailed electron transfer studies indicate that cytochrome C55U and the MADH-amicyanin complex associate in solution (186). The temperature dependence of the rate constant for electron transfer from copper to iron, within this ternary complex, provides estimates of A and Hab of 1.1 eV and 0.3 cm" respectively. These results are consistent with electron transfer over distances of 13-23 A, de-... 

Several copper enzymes will be discussed in detail in subsequent sections of this chapter. Information about major classes of copper enzymes, most of which will not be discussed, is collected in Table 5.1 as adapted from Chapter 14 of reference 49. Table 1 of reference 4 describes additional copper proteins such as the blue copper electron transfer proteins stellacyanin, amicyanin, auracyanin, rusticyanin, and so on. Nitrite reductase contains both normal and blue copper enzymes and facilitates the important biological reaction NO) — NO. Solomon s Chemical Reviews article4 contains extensive information on ligand field theory in relation to ground-state electronic properties of copper complexes and the application of... 

Fig. 6. Electron transfer complex between methylamine dehydrogenase and amicyanin from Paracoccus dentrificans (PDB Accession Code 2MTA). The distance shown is between eN of the redox cofactor tryptophan tryptophylquinone of methylamine dehydrogenase and the eN of the His-95 ligand of amicyanin.

A binary complex of MADH and amicyanin (Chen et al., 1992) and a ternary protein complex of these proteins plus cytochrome c-551i (Chen et al., 1994) from P. denitrificans have been crystallized and their structures have been determined. The structures of the crystallized complexes of these proteins indicate that the interface between MADH and amicyanin is... 

METHYLAMINE DEHYDROGENASE-AMICYANIN-CYTOCHROME c-551i COMPLEX... 

Structure of the MADH-Amicyanin-Cytochrome c-551i Complex... 

A complex of these proteins has been crystallized as a hetero-octamer comprised of one MADH tetramer, two amicyanins and two cytochromes (Chen et al., 1994). The direct distances between redox centers are 9.4 from TTQ to copper, and 23 from copper to heme (Figure 6). 

Unlike the MADH-amicyanin protein interface which was discussed earlier, the amicyanin-cytochrome c-551i interface revealed in the crystal structure of the complex is relatively hydrophilic. The association between proteins appears to be stabilized by several hydrogen bond and ionic interactions (Chen et al., 1994). The shortest gap between the proteins, for consideration of a possible site for interprotein electron transfer, is from the backbone O of Glu of amicyanin to the backbone N of Glyof cytochrome c-551i, a distance of less than 3. ... 

FIGURE 6. Orientation of redox cofactors in the MADH-amicyanin-cytochrome c-551i complex. A portion of the crystal structure is shown with the direct distances between the cofactors indicated. Coordinates are available in the Brookhaven Protein Data Bank, entry 2MTA. 

Chen, L., Durley, R., Mathews, F. S., and Davidson, V. L., 1994, Structure of an electron transfer complex Methylamine dehydrogenase, amicyanin and cytochrome c-551i. Science 264 86990. 

Davidson, V. L., and Jones, L. H., 1995, Complex formation with methylamine dehydrogenase affects the pathway of electron transfer from amicyanin to cytochrome c-551i. J. Biol. Chem. 270 23941A23943. 

Kumar, M. A., and Davidson, V. L., 1990, Chemical cross-linking study of complex formation between methylamine dehydrogenase and amicyanin from Paracoccus denitrificans. Biochemistry, 29 529995304. 

---