Interactions of subunits Asa2, Asa4 and Asa7 in the peripheral stalk of the mitochondrial ATP synthase of the chlorophycean alga Polytomella sp.
Mitochondrial F1FO-ATP synthase of chlorophycean algae is a complex partially embedded in the inner mitochondrial membrane that is isolated as a highly stable dimer of 1600kDa. It comprises 17 polypeptides, nine of which (subunits Asa1 to 9) are not present in classical mitochondrial ATP synthases and appear to be exclusive of the chlorophycean lineage. In particular, subunits Asa2, Asa4 and Asa7 seem to constitute a section of the peripheral stalk of the enzyme. Here, we over-expressed and purified subunits Asa2, Asa4 and Asa7 and the corresponding amino-terminal and carboxy-terminal halves of Asa4 and Asa7 in order to explore their interactions in vitro, using immunochemical techniques, blue native electrophoresis and affinity chromatography. Asa4 and Asa7 interact strongly, mainly through their carboxy-terminal halves. Asa2 interacts with both Asa7 and Asa4, and also with subunit α in the F1 sector. The three Asa proteins form an Asa2/Asa4/Asa7 subcomplex. The entire Asa7 and the carboxy-terminal half of Asa4 seem to be instrumental in the interaction with Asa2. Based on these results and on computer-generated structural models of the three subunits, we propose a model for the Asa2/Asa4/Asa7 subcomplex and for its disposition in the peripheral stalk of the algal ATP synthase.
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F., Mexico.
Héctor
H
Miranda-Astudillo
Araceli
A
Cano-Estrada
Miriam
M
Vázquez-Acevedo
Lilia
L
Colina-Tenorio
Angela
A
Downie-Velasco
Pierre
P
Cardol
Claire
C
Remacle
Lenin
L
Domínguez-Ramírez
Diego
D
González-Halphen
D000595:Amino Acid Sequence; D003198:Computer Simulation; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D008928:Mitochondria / Q000201:enzymology*; D051336:Mitochondrial Membranes / Q000737:chemistry; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D046912:Multiprotein Complexes; D010455:Peptides / Q000737:chemistry*; D021122:Protein Subunits / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D016823:Volvocida / Q000201:enzymology
D046912:Multiprotein Complexes; D010455:Peptides; D021122:Protein Subunits; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases
Asa subunits; Chlamydomonas reinhardtii; Chlorophycean algae; Dimeric mitochondrial complex V; F(1)F(O)-ATP synthase peripheral-stalk; Polytomella sp.