Carboxy-Terminus Recruitment Induced by Substrate Binding in Eukaryotic Fructose Bis-phosphate Aldolases
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- 作者：Julien Lafrance-Vanasse ; Jurgen Sygusch
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：August 21, 2007
- 年：2007
- 卷：46
- 期：33
- 页码：9533 - 9540
- 全文大小：430K
- 年卷期：v.46,no.33(August 21, 2007)
- ISSN：1520-4995
文摘
The crystal structures of Leishmania mexicana fructose-1,6-bis(phosphate) aldolase in complexwith substrate and competitive inhibitor, mannitol-1,6-bis(phosphate), were solved to 2.2 Å resolution.Crystallographic analysis revealed a Schiff base intermediate trapped in the native structure complexedwith substrate while the inhibitor was trapped in a conformation mimicking the carbinolamine intermediate.Binding modes corroborated previous structures reported for rabbit muscle aldolase. Amino acid substitutionof Gly-312 to Ala, adjacent to the P1-phosphate binding site and unique to trypanosomatids, did notperturb ligand binding in the active site. Ligand attachment ordered amino acid residues 359-367 of theC-terminal region (353-373) that was disordered beyond Asp-358 in the unbound structure, revealing anovel recruitment mechanism of this region by aldolases. C-Terminal peptide ordering is triggered byP1-phosphate binding that induces conformational changes whereby C-terminal Leu-364 contacts P1-phosphate binding residue Arg-313. C-Terminal region capture synergizes additional interactions withsubunit surface residues, not perturbed by P1-phosphate binding, and stabilizes C-terminal attachment.Amino acid residues that participate in the capturing interaction are conserved among class I aldolases,indicating a general recruitment mechanism whereby C-terminal capture facilitates active site interactionsin subsequent catalytic steps. Recruitment accelerates the enzymatic reaction by using binding energy toreduce configurational entropy during catalysis thereby localizing the conserved C-terminus tyrosine, whichmediates proton transfer, proximal to the active site enamine.