TY - JOUR

T1 - Cytochrome c Reductase from Potato Does not Comprise Three Core Proteins but Contains an Additional Low‐Molecular‐Mass Subunit

AU - Jänsch, Lothar

AU - Kruft, Volker

AU - Schmitz, Udo

AU - Braun, Hans‐Peter

PY - 1995/3

Y1 - 1995/3

N2 - Analysis of cytochrome c reductase from potato by Tricine/SDS/PAGE reveals 10 bands representing 10 different subunits. In comparison to glycine/SDS/PAGE one additional small protein becomes visible, whereas the three large core proteins are not resolved. The identity of the subunits was determined by immunoblotting and direct sequence determination. Sequence data for the novel small component were used to derive oligonuleotides for probing a potato cDNA‐library and isolating corresponding clones. The newly identified subunit is a 6.7‐kDa protein, that exhibits significant sequence similatity to a 8.5‐kDa subunit of cytochrome c reductase from yeast and the 6.5‐kDa iron‐sulfur‐protein‐binding factor from the equivalent enzyme complex from beef. Also the potato 6.7‐kDa subunit can be dissociated from the cytochrome c reductase complex together with the iron‐sulfur protein. To address the question of whether three or two core subunits occur simultaneously in monomeric cytochrome c reductase complexes from potato, a peptide‐specific antibody was generated. The antiserum is capable of discriminating between the 55‐kDa and 53‐kDa core proteins, which can be separated by glycine/SDS/PAGE and which were previously found to be structurally related. Immunoprecipitations of isolated cytochrome c reductase from potato using this antibody revealed an enzyme complex containing only two core proteins. The simultaneous occurrence of only two core subunits was confirmed by a comparison of the molecular masses of cytochrome c reductase from potato and beef by blue‐native‐gel electrophoresis. Hence the cytochrome c reductase complexes from potato, beef and yeast have a very conserved subunit composition. The evolutionary implications of these findings are discussed.

AB - Analysis of cytochrome c reductase from potato by Tricine/SDS/PAGE reveals 10 bands representing 10 different subunits. In comparison to glycine/SDS/PAGE one additional small protein becomes visible, whereas the three large core proteins are not resolved. The identity of the subunits was determined by immunoblotting and direct sequence determination. Sequence data for the novel small component were used to derive oligonuleotides for probing a potato cDNA‐library and isolating corresponding clones. The newly identified subunit is a 6.7‐kDa protein, that exhibits significant sequence similatity to a 8.5‐kDa subunit of cytochrome c reductase from yeast and the 6.5‐kDa iron‐sulfur‐protein‐binding factor from the equivalent enzyme complex from beef. Also the potato 6.7‐kDa subunit can be dissociated from the cytochrome c reductase complex together with the iron‐sulfur protein. To address the question of whether three or two core subunits occur simultaneously in monomeric cytochrome c reductase complexes from potato, a peptide‐specific antibody was generated. The antiserum is capable of discriminating between the 55‐kDa and 53‐kDa core proteins, which can be separated by glycine/SDS/PAGE and which were previously found to be structurally related. Immunoprecipitations of isolated cytochrome c reductase from potato using this antibody revealed an enzyme complex containing only two core proteins. The simultaneous occurrence of only two core subunits was confirmed by a comparison of the molecular masses of cytochrome c reductase from potato and beef by blue‐native‐gel electrophoresis. Hence the cytochrome c reductase complexes from potato, beef and yeast have a very conserved subunit composition. The evolutionary implications of these findings are discussed.

KW - Cytochrome c reductase

KW - mitochondrial processing peptidase

KW - mitochondrial protein import

KW - respiration

KW - Solanum tuberosum

UR - http://www.scopus.com/inward/record.url?scp=0028934057&partnerID=8YFLogxK

U2 - 10.1111/j.1432-1033.1995.tb20335.x

DO - 10.1111/j.1432-1033.1995.tb20335.x

M3 - Article

C2 - 7737189

AN - SCOPUS:0028934057

VL - 228

SP - 878

EP - 885

JO - European Journal of Biochemistry

JF - European Journal of Biochemistry

SN - 0014-2956

IS - 3

ER -