type	Journal Article
authors	Ehrenreich, A.; Forchhammer, K.; Tormay, P.; Veprek, B.; Bock, A.
title	Selenoprotein synthesis in E. coli. Purification and characterisation of the enzyme catalysing selenium activation
journal	Eur J Biochem
Activity	2.9.1.1
ui	92299004
year	(1992)
volume	206
number	3
pages	767-73.
keywords	Adenosine Triphosphate/metabolism
abstract	The product of the selD gene from Escherichia coli catalyses the formation of an activated selenium compound which is required for the synthesis of Sec-tRNA (Sec, selenocysteine) from Ser-tRNA and for the formation of the unusual nucleoside 5-methylaminomethyl-2-selenouridine in several tRNA species. selD was overexpressed in a T7 promoter/polymerase system and purified to apparent homogeneity. Purified SELD protein is a monomer of 37 kDa in its native state and catalyses a selenium-dependent ATP-cleavage reaction delivering AMP and releasing the beta-phosphate as orthophosphate. The gamma-phosphate group of ATP was not liberated in a form able to form a complex with molybdate. It was precluded that any putative covalent or non-covalent ligand of SELD not removed during purification participated in the reaction. In a double-labelling experiment employing [75Se]selenite plus dithiothreitol and [gamma-32P]ATP the 75Se and 32P radioactivities co-chromatographed on a poly(ethyleneimine)-cellulose column. No radioactivity originating from ATP eluted in this position when [alpha- 32P]ATP or [beta-32P]ATP or [14C]ATP were offered as substrates. The results support the speculation that the product of SELD is a phosphoselenoate with the phosphate moiety derived phosphoselenoate from the gamma-phosphate group of ATP. The alpha,beta cleavage of ATP is also supported by the finding that neither adenosine 5'-[alpha,beta- methylene]triphosphate nor adenosine 5'-[beta,gamma- methylene]triphosphate served as substrates in the reaction.
last changed	2002/11/12 16:17