These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Two states of the nucleotide-binding site of sarcoplasmic reticulum adenosine triphosphatase detected by the calcium-dependent reaction with adenosine 5'-[gamma-imidazolidate]triphosphate and adenosine 5'-[beta-imidazolidate]diphosphate.
    Author: Gutowski-Eckel Z, Bäumert HG.
    Journal: Eur J Biochem; 1993 Dec 15; 218(3):823-8. PubMed ID: 8281933.
    Abstract:
    The Ca(2+)-ATPase from sarcoplasmic reticulum can be inhibited by adenosine 5'-[gamma-imidazolidate]triphosphate through the formation of an intramolecular cross-link at the active site which is dependent on the presence of Ca2+ [Bill, E., Gutowski, Z. & Bämert, H.G. (1988). Calcium-dependent inactivation of the Ca(2+)-ATPase from sarcoplasmic reticulum by chemically reactive adenosine triphosphate, Eur. J. Biochem. 176, 119-124] In the present study we show that adenosine 5'-[beta-imidazolidate]diphosphate is likewise an inhibitor of the Ca(2+)-ATPase effecting a similar inhibition pattern on phosphate release and Ca2+ transport. The overall reaction is Ca2+ dependent and produces a protein band that in SDS/PAGE is indistinguishable from that seen with ATP[imidazolidate]. This shows that the side chain of Asp351 which is claimed to be involved in the cross-linking reaction must be in reach of both the beta and the gamma phosphate moiety of the respective nucleotides. The cross-linked product is formed by a two-step reaction. The first step is the fast reaction of nucleotide imidazolidate presumably at the phosphorylation site (Asp351) under-formation of a mixed anhydride that covalently links nucleotide and protein. Subsequently, the nucleotide is released by a substitution reaction with a second amino acid side chain. This cross-linking reaction is strictly Ca2+ dependent and, remarkably, requires Ca2+ to be added before addition of the inhibitor. It proceeds at two rates and suggests that there are two states of the nucleotide-bindings site. This is also supported by the fact that in the absence of CA2+, ATP[imidazolidate] reacts only in approximately 50% of the calculated ATP-binding sites (based on 80-90% ATPase of total sarcoplasmic reticulum protein) with no subsequent cross-linking reaction.
    [Abstract] [Full Text] [Related] [New Search]