Abstract
A tight coupling between adenosine triphosphate (ATP) hydrolysis and vectorial ion transport has to be maintained by ATP-consuming ion pumps. We report two crystal structures of Ca2+-bound sarco(endo)plasmic reticulum Ca2+-adenosine triphosphatase (SERCA) at 2.6 and 2.9 angstrom resolution in complex with (i) a nonhydrolyzable ATP analog [adenosine (beta-gamma methylene)-triphosphate] and (ii) adenosine diphosphate plus aluminum fluoride. SERCA reacts with ATP by an associative mechanism mediated by two Mg2+ ions to form an aspartyl-phosphorylated intermediate state (Ca2-E1 approximately P). The conformational changes that accompany the reaction with ATP pull the transmembrane helices 1 and 2 and close a cytosolic entrance for Ca2+, thereby preventing backflow before Ca2+ is released on the other side of the membrane.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Adenosine Diphosphate / metabolism
-
Adenosine Triphosphate / analogs & derivatives*
-
Adenosine Triphosphate / metabolism*
-
Aluminum Compounds / metabolism
-
Animals
-
Binding Sites
-
Calcium / metabolism*
-
Calcium-Transporting ATPases / chemistry*
-
Calcium-Transporting ATPases / metabolism*
-
Crystallization
-
Crystallography, X-Ray
-
Cytosol / metabolism
-
Fluorides / metabolism
-
Models, Molecular
-
Muscle Fibers, Fast-Twitch / enzymology*
-
Phosphorylation
-
Protein Conformation
-
Protein Structure, Secondary
-
Protein Structure, Tertiary
-
Rabbits
-
Sarcoplasmic Reticulum Calcium-Transporting ATPases
Substances
-
Aluminum Compounds
-
5'-adenylyl (beta,gamma-methylene)diphosphonate
-
Adenosine Diphosphate
-
Adenosine Triphosphate
-
Sarcoplasmic Reticulum Calcium-Transporting ATPases
-
Calcium-Transporting ATPases
-
Fluorides
-
Calcium
-
aluminum fluoride