TY - JOUR

T1 - Molecular structure of the 8.0 kDa subunit of cytochrome-c reductase from potato and its Δψ-dependent import into isolated mitochondria

AU - Braun, Hans Peter

AU - Schmitz, Udo K.

N1 - Funding information: We wish to thank Dr. V. Kruft for the determination of the N-terminal sequence of the potato 8.0 kDa protein and H. Mentzel for excellent technical assistance. This work was supported by the Deutsche Forschungsgemeinschaft, grant Schm. 698/2 and by the BMFT.

PY - 1995/4/26

Y1 - 1995/4/26

N2 - The cytochrome-c reductase (EC 1.10.2.2) of the mitochondrial respiratory chain couples electron transport from ubiquinol to cytochrome c with proton translocation across the inner mitochondrial membrane. The enzyme from potato was shown to be composed of 10 subunits. Isolation and characterization of cDNA clones for the second smallest subunit reveal an open reading frame of 216 bp encoding a protein of 8.0 kDa. The protein exhibits similarities to a 7.2/7.3 kDa subunit of cytochrome-c reductase from bovine and yeast, that is localized on the intermembrane space side of the enzyme complex. It also shows similarity to a previously unidentified 7.8 kDa protein of cytochrome-c reductase from Euglena. The potato 8.0 kDa protein has a segmental structure, as its sequence can be devided into four parts, each comprising a central Arg-(Xaa)5-Val motif. N-terminal sequencing of the mature 8.0 kDa protein indicates the absence of a cleavable mitochondrial targeting sequence. Import of the in vitro synthesized 8.0 kDa protein into isolated potato mitochondria confirms the lack of a presequence and reveals a dependence of the transport on the membrane potatial Δψ across the inner mitochondrial membrane. These features are unique among the intermembrane space proteins known so far.

AB - The cytochrome-c reductase (EC 1.10.2.2) of the mitochondrial respiratory chain couples electron transport from ubiquinol to cytochrome c with proton translocation across the inner mitochondrial membrane. The enzyme from potato was shown to be composed of 10 subunits. Isolation and characterization of cDNA clones for the second smallest subunit reveal an open reading frame of 216 bp encoding a protein of 8.0 kDa. The protein exhibits similarities to a 7.2/7.3 kDa subunit of cytochrome-c reductase from bovine and yeast, that is localized on the intermembrane space side of the enzyme complex. It also shows similarity to a previously unidentified 7.8 kDa protein of cytochrome-c reductase from Euglena. The potato 8.0 kDa protein has a segmental structure, as its sequence can be devided into four parts, each comprising a central Arg-(Xaa)5-Val motif. N-terminal sequencing of the mature 8.0 kDa protein indicates the absence of a cleavable mitochondrial targeting sequence. Import of the in vitro synthesized 8.0 kDa protein into isolated potato mitochondria confirms the lack of a presequence and reveals a dependence of the transport on the membrane potatial Δψ across the inner mitochondrial membrane. These features are unique among the intermembrane space proteins known so far.

KW - (S. tuberosum)

KW - bc complex

KW - Cytochrome-c reductase

KW - Mitochondrion

KW - Protein transport

KW - Respiratory chain

UR - http://www.scopus.com/inward/record.url?scp=0028910492&partnerID=8YFLogxK

U2 - 10.1016/0005-2728(94)00199-F

DO - 10.1016/0005-2728(94)00199-F

M3 - Article

C2 - 7727497

AN - SCOPUS:0028910492

VL - 1229

SP - 181

EP - 186

JO - BBA - Bioenergetics

JF - BBA - Bioenergetics

SN - 0005-2728

IS - 2

ER -