ISSN:
1573-4919
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary Dimethyl suberimidate and dithiobis (succinimidyl propionate) have been used to explore the nearest neighbor relationship of the subunits (α, β, γ and δ by decreasing molecular weight) of F1-ATPase or BF1 factor of Micrococcus lysodeikticus. Cross-linking with the two diimido esters inhibited the ATPase activity but this inhibition never exceeded 50% of the initial value. The cross-linking pattern of this BF1 factor, as revealed by sodium dodecyl sulfate gel electrophoresis, shows a relative low proportion of high molecular weight aggregates which move slowly than the heaviest subunit (α). They are resolved as three components of molecular weights 200,000, 130,000 and 100,000 in 5% acrylamide gels, plus an additional component (mol. wt 80,000) identified in 10% acrylamide gels. The other aggregate bands represent cross-linking products of the smaller subunits (γ and δ) that may travel to the conventional position of the heavier subunits. The subunit composition of the aggregate bands has been determined through the reversion of dithiobis (succinimidyl propionate) cross-linking of the BF1 factor by dithiothreitol and analysis in second dimension by gel electrophoresis. The results indicate that γ subunit can cross-link with itself and with each of the other subunits except β. The α subunit is also able to cross-link with itself and with the other subunits although to a minor extent than γ, and that δ2 aggregates are present. These results represent a specific pattern of cross-linking for this BF1 factor as compared to other F1 coupling factors. It suggests a certain asymmetry in the spatial organization of the major subunits of M. lysodeikticus F1-ATPase where the γ subunit must play a central role. A subunit stoichiometry α3 β3 γ2 δ2 is proposed for whole F1-ATPase which leads to a molecular weight 440,000 consistent with the 430,000 value estimated by sedimentation equilibrium at low speed. A tentative structural model of M. lysodeikticus BF1 factor is derived from these data. The significance of the results in relation to the possible generalization of the molecular architecture of F1 factors is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00224567
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