Figure 1.

Subunit composition of CcO before and after exposure to various concentrations of urea. In each sample, dodecylmaltoside solubilized CcO was exposed to 0 - 7 urea for 2 hr at room temperature, the dissociated subunits and urea were removed by HiTrap Q anion exchange chromatography, and the subunit composition determined by either SDS-PAGE or reversed phase HPLC. Top Panel: SDS-PAGE analysis of the mitochondrial-encoded subunit composition CcO before and after exposure to 0, 3.0, 5.0 and 7.0 M urea. Bottom Panel: Reversed-phase C₁₈-HPLC subunit analysis of the nuclear-encoded subunit composition determined by analysis of 100μg (0.5 nmol) of the purified CcO using reversed-phase C₁₈ HPLC (refer to Methods for details). Elution peaks are labeled by roman numerals to indicate the elution peak corresponding to each of the nuclear-encoded subunits. The four elution profiles from the top down correspond to results obtained after exposure to 0, 4.0, 5.5, and 7.0 M urea, and are labeled accordingly. Prolonged incubation at high urea concentrations did not affect either the elution position or the shape of the elution peaks suggesting that covalent modification by urea break down products, e.g., cyanate, did not occur.