Spectroscopic characterization of native and Co(II)-substituted zucchini mavicyanin

Novel EPR signals associated with FeMoco centres of MoFe protein in MgADP‐inhibited turnover of nitrogenase

“…Cp2 remains oxidised at prolonged reaction times, even in the presence of excess dithionite. It has previously been shown that two Cp2 molecules are tightly complexed to Kp1 under these conditions and that the predominant species during enzyme turnover is (Cp2 ADPox ) 2 Kp1, but no time dependence of the EPR were reported [15]. The absence of the characteristic EPR signal of Cp2 after 1 h incubation ( Fig.…”

“…When turnover is initiated, protons are reduced without a lag, C 2 H 2 is not reduced initially, but becomes an e¡ective substrate after 10 min, [13], and a 30 min lag occurs before N 2 is reduced to NH 3 [14]. There is currently no explanation for this behaviour, but recently we demonstrated that, unlike homologous Kp-nitrogenase components, Cp2 and Kp1 form a stable 1:1 complex which can be isolated by gel ¢ltration, both in the presence and absence of MgATP [15]. This stable complex is unusual, since although the Cp2 is bound to Kp1, it is reduced as indicated by the presence of a characteristic S = 1/2 EPR spectrum of Cp2 in the [4Fe^4S] 1 oxidation level [16].…”

“…3.3. Turnover of homologous Kp-nitrogenase leads to the formation of the novel S = 3/2 EPR signals The formation of these novel signals does not arise from the unusual properties of Cp2Kp1-nitrogenase in forming a stable 1:1 complex [15], since they are also developed by turnover of homologous Kp-nitrogenase. Fig.…”

Measurement of electric field gradient at 117In on the Cu-site in mavicyanin by perturbed angular correlation of γ-rays

“…Mavicyanin isolated from zucchini peelings is a member of the cupredoxin family or blue copper protein, but its physiological role in plants is still unknown [1][2][3]. The protein was found to have a copper ion coordinated with two His, one Cys residues and a Gln residue with an amide-oxygen atom as shown in Figure1 [3].…”

Crystallization and preliminary X-ray crystallographic studies of mavicyanin fromCucurbita pepo medullosa

“…Mavicyanin isolated from Cucurbita pepo medullosa (zucchini) peel is a member of the family of proteins known as cupredoxins (Marchesini et al, 1979;Maritano et al, 1997). Proteins in this family are characterized by an intense electronic absorption band near 600 nm, which gives them their characteristic blue to green-blue colour, and unusual small hyper®ne coupling constants in their EPR spectra.…”