ISSN:
0091-7419
Keywords:
Life Sciences
;
Molecular Cell Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Highly purified preparations of Streptococcus faecalis ATPase contain a similar but inactive protein detected by prolonged polyacrylamide gel electrophoresis. The inactive protein appears to arise by proteolytic cleavage of the major subunits in the enzyme. By use of a new technique, subunit analysis in SDS gels was performed on the enzyme band and the inactive protein band excised from a polyacrylamide gel after electrophoresis. The results indicated that the ATPase has the composition α3β3γ in which α = 60,000, β = 55,000, and γ = 37,000 daltons. The inactive protein appears to have the composition (f)6 in which f = 49,000 daltons. There is also evidence that the enzyme band contains some slightly modified forms of the ATPase, such as α3β2 (f)γ. The inactive protein lacks the capacity for tight nucleotide binding.Our experiments show that the tight ATPase-nucleotide complex formed in S. faecalis cells (the endogenous complex) behaves differently from the tight complex formed in vitro (the exogenous complex). We prepared a doubly labeled complex containing endogenous 32P-labeled ADP and ATP and exogenous 3H-labeled ADP. We observed that the addition of free nucelotide to the doubly labeled ATPase displaced the exogenous bound ligand from the enzyme but not the endogenous bound nucleotide. We suggest that the displaceable and nondisplaceable forms of the tight ATPase-nucleotide complex correspond to two different conformational states of the enzyme.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jss.400030309
