2.9.1.2	A239T	naturally occurring mutation and site-directed mutagenesis. The mutant forms a stable complex with GroEL. Residue Ala239 is located in helix alpha8 near the site that interacts with the variable arm of tRNASec, and is distant from the active site. The A239T variant binds tRNASec with less affinity compared to wild-type SepSecS, but its catalytic function is unaffected	762417	
2.9.1.2	H166A	the mutant is partially active in forming Sec-tRNASec in vivo. In vitro, the mutant is partially active in forming Cys-tRNASec	694428	
2.9.1.2	H166F	mutant is inactive in vivo	694428	
2.9.1.2	H166Q	mutant is inactive in vivo	694428	
2.9.1.2	K173A	in vivo activity of the mutant is indistinguishable from that of the wild-type enzyme	695136	
2.9.1.2	K173M	in vivo activity of the mutant is indistinguishable from that of the wild-type enzyme	695136	
2.9.1.2	additional information	mapping pathogenic mutations onto the tetrameric human SepSecS-tRNASec complex, overview	762417	
2.9.1.2	Q105A	mutant is inactive in vivo	695136	
2.9.1.2	R307A	the mutant is significantly less active in L-selenocysteinyl-tRNASec formation in vivo and Cys-tRNASec formation in vitro	694428	
2.9.1.2	R313A	mutant is inactive in vivo	695136	
2.9.1.2	R72A	the mutant enzyme is significantly less active in L-selenocysteinyl-tRNASec formation in vivo and Cys-tRNASec formation in vitro. The mutant enzyme is unable to form L-selenocysteinyl-tRNASec in vitro	694428	
2.9.1.2	R75A	mutant is inactive in vivo	695136	
2.9.1.2	R97A	in vivo activity of the mutant is indistinguishable from that of the wild-type enzyme	695136	
2.9.1.2	R97Q	in vivo activity of the mutant is indistinguishable from that of the wild-type enzyme	695136	
2.9.1.2	T325S	naturally occurring mutation and site-directed mutagenesis, the mutation does not affect the binding affinity of the SepSecS-tRNA complex. The mutant does not form a complex with GroEL. Residue Thr325 is located in helix alpha12 and about 15 A away from the active site. The Thr325 to Ser replacement does not cause any changes in the tetrameric structure of SepSecS. Tetramers of T325S adopt the same structure as wild-type SepSecS. The pathogenic mutation Thr325Ser does not alter the three-dimensional structure of the SepSecS tetramer	762417	
2.9.1.2	Y334C	naturally occurring mutation and site-directed mutagenesis, the mutation does not affect the binding affinity of the SepSecS-tRNA complex. The mutant forms a stable complex with GroEL. The side chain of Tyr334 is in helix alpha13 near the active-site pocket. Its hydroxyl group forms a hydrogen bond with the backbone carbonyl of Asn285, and this interaction may help stabilize a loop that carries Lys284 and the covalently attached PLP cofactor. In the Y334C crystal, the side chain of Cys334 coordinates two water molecules, which interact with the backbone carbonyl of Asn285 in the same fashion as the Tyr side chain in the wild-type enzyme. Tetramers of Y334C adopt the same structure as wild-type SepSecS. The pathogenic mutation Tyr334Cys does not alter the three-dimensional structure of the SepSecS tetramer	762417	
2.9.1.2	Y429*	naturally occurring nonsense mutation and site-directed mutagenesis. Y429* expresses at low levels and as insoluble protein regardless of the incubation temperature, induction point, or the growth media used. Tyr429 is located before strand beta14. Premature abortion of protein synthesis yields a truncated enzyme devoid of strand beta14, loop beta14-alpha15, and the C-terminal helix alpha15. Loop beta14-alpha15 establishes a side of the catalytic groove, and helix alpha15 provides residues that bind the 5'-end of tRNASec. The Y429* variant is not be capable of promoting selenocysteine synthesis	762417