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Isolation and characterisation of a functional αβ heterodimer from the ATP synthase of Rhodospirillum rubrum
Author(s) -
Andralojc P.J.,
Harris D.A.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)81326-h
Subject(s) - rhodospirillum rubrum , dimer , atp hydrolysis , chemistry , atpase , atp synthase , sodium azide , chromatophore , enzyme , biochemistry , biophysics , ion , stereochemistry , biology , organic chemistry , fishery
An αβ heterodimer of the F 1 ‐ATPase of Rhodospirillum rubrum was isolated by extraction of chromatophores with LiCl. Each αβ heterodimer contains one tightly bound ADP, which is released upon removal of medium Mg 2+ . The dimer can be reversibly dissociated by removal of Mg 2+ ‐ions. The αβ heterodimer restores both ATP‐synthetic and hydrolytic activities to LiCl‐treated chromatophores, saturation being achieved at approximately 2 mmol αβ · mol BChl −1 . The heterodimer itself hydrolyses Mg‐ATP with an activity distinct from RF 1 , being unaffected by azide or sulphite ions. The V max and K m (ATP) for this Mg 2+ ‐dependent activity were 110 ± 10 nmol · min −1 mg protein −1 and 100 ± 30 μM, respectively. The K m did not differ significantly from that of RF 1 .