PDBsum entry 2j4f

Hydrolase

PDB id: 2j4f

Contents

Protein chain

527 a.a. *

Metals

_HG ×2

Waters ×94

* Residue conservation analysis

PDB id:

2j4f

Name:

Hydrolase

Title:

Torpedo acetylcholinesterase - hg heavy-atom derivative

Structure:

Acetylcholinesterase. Chain: a. Fragment: residues 22-564. Synonym: ache. Ec: 3.1.1.7

Source:

Torpedo californica. Pacific electric ray. Organism_taxid: 7787

Resolution:

2.80Å R-factor: 0.204 R-free: 0.262

Authors:

D.I.Kreimer,E.A.Dolginova,M.Raves,J.L.Sussman,I.Silman,L.Weiner

Key ref:

D.I.Kreimer et al. (1994). A metastable state of Torpedo californica acetylcholinesterase generated by modification with organomercurials. Biochemistry, 33, 14407-14418. PubMed id: 7981200 DOI: 10.1021/bi00252a006

Date:

30-Aug-06 Release date: 05-Sep-06

Protein chain

P04058  (ACES_TETCF) -  Acetylcholinesterase from Tetronarce californica

Seq: 586 a.a.

Struc: 527 a.a.

Enzyme reactions

• Enzyme class: E.C.3.1.1.7 - acetylcholinesterase.
• Reaction: acetylcholine + H2O = choline + acetate + H⁺

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1021/bi00252a006

Biochemistry 33:14407-14418 (1994)

PubMed id: 7981200

A metastable state of Torpedo californica acetylcholinesterase generated by modification with organomercurials.

D.I.Kreimer, E.A.Dolginova, M.Raves, J.L.Sussman, I.Silman, L.Weiner.

ABSTRACT

Chemical modification of Torpedo californica acetylcholinesterase by various sulfhydryl reagents results in its conversion to one of two principal states. One of these states, viz., that produced by disulfides and alkylating agents, is stable. The second state, produced by mercury derivatives, is metastable. At room temperature, it converts spontaneously, with a half-life of ca. 1 h, to a stable state similar to that produced by the disulfides and alkylating agents. Demodification of acetylcholinesterase freshly modified by mercurials, by its exposure to reduced glutathione, causes rapid release of the bound mercurial, with concomitant recovery of most of the enzymic activity of the native enzyme. In contrast, similar demodification of acetylcholinesterase modified by disulfides yields no detectable recovery of enzymic activity. Spectroscopic measurements, employing CD, intrinsic fluorescence, and binding of 1-anilino-8-naphthalenesulfonate, show that the state produced initially by mercurials is "native-like", whereas that produced by disulfides and alkylating agents, and after prolonged incubation of the mercurial-modified enzyme, is partially unfolded and displays many of the features of the "molten globule" state. Arrhenius plots show that the quasi-native state produced by organomercurials is separated by a low (5 kcal/mol) energy barrier from the native state, whereas the partially unfolded state is separated from the quasi-native state by a high energy barrier (ca. 50 kcal/mol). Comparison of the 3D structures of native acetylcholinesterase and of a heavy-atom derivative obtained with HgAc2 suggests that the mercurial-modified enzyme may be stabilized by additional interactions of the mercury atom attached to the free thiol group of Cys231, specifically with Ser228O gamma with the main-chain nitrogen and carbonyl oxygen of the same serine residue.