Methanococcus vannielii Selenium Metabolism: Purification and N‐terminal Amino Acid Sequences of a Novel Selenium‐binding Protein and Selenocysteine Lyase

Abstract

SummarySelenium is an essential component of several enzymes and proteins in a number of methane-producing archae. Information concerning accessory proteins that function in selenium transport processes, however, is limited. A novel selenium-binding protein with a potential transport role and a selenocysteine lyase that serves as a selenium delivery protein are present in Methanococcus vannielii. The selenium-binding protein was purified from extracts of 75 Selabeled cells. Although there was gradual loss of 75 Se during purification, the isolated protein still could be detected as a radioactive 42 kDa species on native PAGE gels and as a 33 kDa species on SDS PAGE gels. The N-terminal amino acid sequence of residues 1 -63 of the protein was determined by automated Edman degradative analysis. The only homologous sequence detected in the recorded data base was that of a gene encoding an unknown protein located in the genomic sequence of Methanococcus maripaludis. Cloning and expression of the corresponding gene from M. vannielii are described in a manuscript in press (Self et al.). A 47 kDa selenocysteine lyase isolated from M. vannielii extracts exhibited sequence homology to the NIFS family of proteins that transport sulfur. The purified selenocysteine lyase catalyzed the elimination of an elemental form of selenium from free selenocysteine and delivered this selenium directly to selenophosphate synthetase. The synthetase converted the selenium to selenophosphate in an ATP-dependent reaction.

Selenoproteins: Molecular Pathways and Physiological Roles

“…Recently, SCL has been shown to be involved in selenoprotein synthesis in vivo in cell culture (193). In addition, in vitro experiments demonstrated that both SPS1 and SPS2 interact with SCL (343) and that bacterial SCL proteins could provide Se to SPS from free Sec, to produce selenophosphate (201,324). These data implicate SCL in the recycling of Se and selenoprotein synthesis.…”

Functional analysis of Arabidopsis genes involved in mitochondrial iron–sulfur cluster assembly

“…NifS/IscS/SufS-like proteins are also known to abstract Se from selenocysteine (Lacourciere et al 2000;Pilon-Smits et al 2002;Stadtman, 2004), with physiological roles in tRNA and formate dehydrogenase H maturation in bacteria and in the detoxification of selenium in plants Van Hoewyk et al 2005). Thus this family of proteins appears to play a broad role in the mobilization of S and Se within cells.…”

Solution NMR Structure of Selenium-binding Protein from Methanococcus vannielii

“…Several of the long range NOEs obtained from four-dimensional 13 C/ 13 C-edited NOESY experiment using uniformly 15 , were also detected in three-dimensional 13 C-edited, 12 Cfiltered NOESY experiments using the mixture of 13 C-labeled subunit and unlabeled subunit, and therefore included in the calculation as intersubunit contacts. The structures converged to a single conformation (Fig.…”

“…In Methanococcus vannielii, the gene corresponding to a family member of these proteins encodes an 8.8-kDa polypeptide. This protein was purified from the organism as a 42-kDa protein and referred to as the selenium-binding protein (SeBP) 3 (12,13). The recombinant protein was shown to bind selenium when the trace element was added to the growth media of the E. coli.…”