Oligomycin sensitivity-conferring protein (OSCP) of mitochondrial ATP synthase. The carboxyl-terminal region of OSCP is essential for the reconstitution of oligomycin-sensitive H(+)-ATPase.

Oligomycin Sensitivity Conferring Protein (OSCP) of Bovine Heart Mitochondrial ATP Synthase: High-Affinity OSCP−Fo Interactions Require a Local α-Helix at the C-Terminal End of the Subunit

“…As pointed out in an earlier section, a mutant form of bovine OSCP lacking the last 10 residues (K181-L190) from the carboxyl end has been shown to be incompetent in its ability to couple proton movements in F o with the catalytic site events at F 1 in the reconstituted F 1 F o ATP synthase preparations (Joshi et al, 1992(Joshi et al, , 1996. Since this region of OSCP is predicted to have a high propensity to form a helix and since it is also known to harbor four conserved charged residues, selected residues in the K181-L190 region of OSCP were replaced by helix-breaking proline(s) or by uncharged but polar glutamine(s) or apolar alanines (see Table 1 for a list of the mutants).…”

“…According to secondary structure prediction algorithms, there are six consensus helical segments in the sequences of bovine OSCP as well as subunit δ which correspond to residues 14-24, 26-51, 61-71, 100-113, 125-140, and 178-186 in bovine OSCP (Engelbrecht et al, 1991). The last segment corresponding to positions 178-186 in bovine OSCP and positions 170-178 in E. coli δ is of interest in the context of oxidative phosphorylation since mutant forms harboring a deletion of this particular segment were found to be impaired with respect to their energy coupling function (Jounouchi et al, 1992;Joshi et al, 1992Joshi et al, , 1996. In addition, multiple sequence alignment of OSCP from various sources revealed that there are four charged residues within the K181-L190 region which correspond to positions 181, 184, 187, and 188 in all sequences.…”

“…The resultant construct, pRKOSCP WT, yielded 50-80 mg of purified WT form of OSCP per liter of cell culture using E. coli strain BL21(DE3) as the host. Amino acid replacements were carried out according to a PCR protocol (Joshi et al, 1992). The final plasmid constructs were characterized by sequencing the entire OSCP gene as well as subcloning sites.…”

“…It is clear from data in rows 1 and 2 that the AE particles prepared at pH 9.8 have quite low exchange activity even upon supplementation with F 1 -ATPase (row 1), but get stimulated by a factor of at least 10 upon addition of OSCP (row 2). This demonstrates that pH 9.8 particles are highly suitable for assaying the biological activity of OSCP [see also Joshi et al (1992Joshi et al ( , 1996].…”

“…In our efforts to get a better understanding of the role of OSCP in mitochondrial energy coupling, we initiated a systematic study to localize domains of OSCP of functional and/ structural importance using nested deletion strategy. Our preliminary studies showed that residues E188-L190 at the C-terminal end of OSCP could be deleted without compromising the energy coupling efficiency of this subunit but mutant forms lacking more than three amino acid residues from the C-terminus were neither able to bind to F o nor restore ATP synthesis activity in OSCP-depleted F 1 F o complexes (Joshi et al, 1992(Joshi et al, . 1994(Joshi et al, , 1996.…”