User:Jamie Abbott/Sandbox2

From Proteopedia

proteopedia linkproteopedia link

Contents 1 Histidyl-tRNA Synthetase 2 Mechanism 3 Evolutionary Conservation 3.1 Structural Homology 4 3D Structures of Histidyl-tRNA Synthetase 5 References

Histidyl-tRNA Synthetase

Histidyl tRNA Synthetase (HisRS) is a 94kD that belongs to the class II of aminoacyl-tRNA synthetases (aaRS). Aminoacyl-tRNA synthetases have been partitioned into two classes, containing 10 members, on the basis of sequence comparisons^[1]. Class I and Class II differ mainly with respect to the topology of the catalytic fold and site of esterification on cognate tRNA^[1]. Class II enzymes have a composed of anti-parallel β-sheets and α-helices (residues 1-325). Additionally, class II enzymes can be further divided into three subgroups: class IIa, distinguished by an N-terminal catalytic domain and C-terminal accessory domain (later shown to be anticodon binding domain); class IIb, whose anticodon binding domain is located on the N-terminal side of the fold; and class IIc, encompassing the tetrameric PheRS and GlyRS class II synthetases.^[2]

Function and Catalysis

spinqualitylabelsall models Structure of Histidyl-tRNA Synthetase (PDB entry 1KMM) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image Class II aminoacyl-tRNA synthetases aminoacylate the 3'OH of their cognate tRNAs. The active site to HisRS contains a histidine binding pocket composed of highly conserved residues found in distinct sequences motifs. First, the LV/AAGGGLDYY loop (or ) forms one wall of the binding pocket. This HisA loop is highly conserved and extends over a part of the active site[3]. Second, the glycine-rich β-strand (sequence AGGRYDGL preceding ) comprises the histidine binding pocket floor and wall. Finally, conserved side chains that make direct contact with histidine are Glu83 and Gly127 (), which contact the α-amino and α-carbonyl functional groups, respectively, and Glu131 (motif II) and Tyr264, which make hydrogen bonds to the Nδ and Nε, respectively, of the imidazole ring[3].

---

---

Mechanism

tRNA

---

Evolutionary Conservation

Structural Homology

3D Structures of Histidyl-tRNA Synthetase

1KMN

1KMM

1HTT

2EL9

---

References

1. ↑ ^{1.0 1.1} Eriani G, Delarue M, Poch O, Gangloff J, Moras D. Partition of tRNA synthetases into two classes based on mutually exclusive sets of sequence motifs. Nature. 1990 Sep 13;347(6289):203-6. PMID:2203971 doi:http://dx.doi.org/10.1038/347203a0
2. ↑ Cusack S, Hartlein M, Leberman R. Sequence, structural and evolutionary relationships between class 2 aminoacyl-tRNA synthetases. Nucleic Acids Res. 1991 Jul 11;19(13):3489-98. PMID:1852601
3. ↑ ^{3.0 3.1} Francklyn, C., and Arnez, J.G. (2004) in Aminoacyl-tRNA Synthetases (Ibba, M.,Francklyn, C.,Cusack, S.. Eds.) Landes Publishing, Austin, TX