MF_01850

tRNA-cytidine(32) 2-sulfurtransferase [ttcA]

HAMAP entry
Member databaseHAMAP
HAMAP typefamily
Short nameTtcA

Description
Imported from IPR012089

This entry represents tRNA-cytidine(32) 2-sulfurtransferase (also known as 2-thiocytidine tRNA biosynthesis protein, TtcA) and its homologues.

The aminoacyl-tRNA synthetases (also known as aminoacyl-tRNA ligases) catalyse the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction
[4, 3]
. These proteins differ widely in size and oligomeric state, and have limited sequence homology
[8]
. The 20 aminoacyl-tRNA synthetases are divided into two classes, I and II. Class I aminoacyl-tRNA synthetases contain a characteristic Rossman fold catalytic domain and are mostly monomeric
[7]
. Class II aminoacyl-tRNA synthetases share an anti-parallel β-sheet fold flanked by α-helices
[2]
, and are mostly dimeric or multimeric, containing at least three conserved regions
[10, 9, 1]
. However, tRNA binding involves an α-helical structure that is conserved between class I and class II synthetases. In reactions catalysed by the class I aminoacyl-tRNA synthetases, the aminoacyl group is coupled to the 2'-hydroxyl of the tRNA, while, in class II reactions, the 3'-hydroxyl site is preferred. The synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan, valine, and some lysine synthetases (non-eukaryotic group) belong to class I synthetases. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, phenylalanine, proline, serine, threonine, and some lysine synthetases (non-archaeal group), belong to class-II synthetases. Based on their mode of binding to the tRNA acceptor stem, both classes of tRNA synthetases have been subdivided into three subclasses, designated 1a, 1b, 1c and 2a, 2b, 2c
[6]
.

tRNA-cytidine(32) 2-sulfurtransferase (also known as 2-thiocytidine tRNA biosynthesis protein TtcA) is required for the thiolation of cytidine in position 32 of tRNA, to form 2-thiocytidine (s(2)C32). The modified nucleoside 2-thiocytidine (s(2)C) has so far been found in tRNA from archaea and bacteria. The TtcA protein family is characterised by the existence of both a PP-loop and a Cys-X(1)-X(2)-Cys motif in the central region of the protein but can be divided into two distinct groups based on the presence and location of additional Cys-X(1)-X(2)-Cys motifs in terminal regions of the sequence. Mutant analysis showed that both cysteines in this central conserved Cys-X(1)-X(2)-Cys motif are required for the formation of s(2)C
[5]
.

References
Imported from IPR012089

1.Sequence, structural and evolutionary relationships between class 2 aminoacyl-tRNA synthetases. Cusack S, Hartlein M, Leberman R. Nucleic Acids Res. 19, 3489-98, (1991). View articlePMID: 1852601

2.Structural basis for transfer RNA aminoacylation by Escherichia coli glutaminyl-tRNA synthetase. Perona JJ, Rould MA, Steitz TA. Biochemistry 32, 8758-71, (1993). View articlePMID: 8364025

3.Aminoacyl-tRNA synthetases: versatile players in the changing theater of translation. Francklyn C, Perona JJ, Puetz J, Hou YM. RNA 8, 1363-72, (2002). View articlePMID: 12458790

4.Aminoacyl-tRNA synthetases, the genetic code, and the evolutionary process. Woese CR, Olsen GJ, Ibba M, Soll D. Microbiol. Mol. Biol. Rev. 64, 202-36, (2000). View articlePMID: 10704480

5.The conserved Cys-X1-X2-Cys motif present in the TtcA protein is required for the thiolation of cytidine in position 32 of tRNA from Salmonella enterica serovar Typhimurium. Jager G, Leipuviene R, Pollard MG, Qian Q, Bjork GR. J. Bacteriol. 186, 750-7, (2004). View articlePMID: 14729701

6.Evolution of aminoacyl-tRNA synthetases--analysis of unique domain architectures and phylogenetic trees reveals a complex history of horizontal gene transfer events. Wolf YI, Aravind L, Grishin NV, Koonin EV. Genome Res. 9, 689-710, (1999). View articlePMID: 10447505

7.The 2.0 A crystal structure of Thermus thermophilus methionyl-tRNA synthetase reveals two RNA-binding modules. Sugiura I, Nureki O, Ugaji-Yoshikawa Y, Kuwabara S, Shimada A, Tateno M, Lorber B, Giege R, Moras D, Yokoyama S, Konno M. Structure 8, 197-208, (2000). View articlePMID: 10673435

8.Partition of tRNA synthetases into two classes based on mutually exclusive sets of sequence motifs. Eriani G, Delarue M, Poch O, Gangloff J, Moras D. Nature 347, 203-6, (1990). View articlePMID: 2203971

9.Classes of aminoacyl-tRNA synthetases and the establishment of the genetic code. Schimmel P. Trends Biochem. Sci. 16, 1-3, (1991). View articlePMID: 2053131

10.The aminoacyl-tRNA synthetase family: modules at work. Delarue M, Moras D. Bioessays 15, 675-87, (1993). View articlePMID: 8274143

Further reading

11. A P-loop-like motif in a widespread ATP pyrophosphatase domain: implications for the evolution of sequence motifs and enzyme activity. Bork P, Koonin EV. Proteins 20, 347-55, (1994). View articlePMID: 7731953

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