PDBsum entry 1enr

Plant lectin (agglutinin)

PDB id: 1enr

Contents

Protein chain

237 a.a. *

Metals

_ZN

_CA

Waters ×141

* Residue conservation analysis

PDB id:

1enr

Name:

Plant lectin (agglutinin)

Title:

Co-crystals of demetallized concanavalin a with zinc and calcium having a zinc ion bound in the s1 site and a calcium ion bound in the s2 site

Structure:

Concanavalin a. Chain: a. Synonym: con a. Other_details: zinc/calcium complex

Source:

Canavalia ensiformis. Jack bean. Organism_taxid: 3823

Biol. unit:

Tetramer (from PQS)

Resolution:

1.83Å R-factor: 0.176

Authors:

J.Bouckaert,R.Loris,F.Poortmans,L.Wyns

Key ref:

J.Bouckaert et al. (1996). Sequential structural changes upon zinc and calcium binding to metal-free concanavalin A. J Biol Chem, 271, 16144-16150. PubMed id: 8663112 DOI: 10.1074/jbc.271.27.16144

Date:

20-Mar-96 Release date: 17-Aug-96

Protein chain

P02866  (CONA_CANEN) -  Concanavalin-A from Canavalia ensiformis

Seq: 290 a.a.

Struc: 237 a.a.*

* PDB and UniProt seqs differ at 26 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1074/jbc.271.27.16144

J Biol Chem 271:16144-16150 (1996)

PubMed id: 8663112

Sequential structural changes upon zinc and calcium binding to metal-free concanavalin A.

J.Bouckaert, F.Poortmans, L.Wyns, R.Loris.

ABSTRACT

The lectin concanavalin A (ConA) sequentially binds a transition metal ion in the metal-binding site S1 and a calcium ion in the metal-binding site S2 to form its saccharide-binding site. Metal-free ConA crystals soaked with either Zn2+ (apoZn-ConA) or Co2+ (apoCo-ConA) display partial binding of these ions in the proto-transition metal-binding site, but no further conformational changes are observed. These structures can represent the very first step in going from metal-free ConA toward the holoprotein. In the co-crystals of metal-free ConA with Zn2+ (Zn-ConA), the zinc ion can fully occupy the S1 site. The positions of the carboxylate ligands Asp10 and Asp19 that bridge the S1 and S2 sites are affected. The ligation to Zn2+ orients Asp10 optimally for calcium ligation and stabilizes Asp19 by a hydrogen bond to one of its water ligands. The neutralizing and stabilizing effect of the binding of Zn2+ in S1 is necessary to allow for subsequent Ca2+ binding in the S2 site. However, the S2 site of monometallized ConA is still disrupted. The co-crystals of metal-free ConA with both Zn2+ and Ca2+ contain the active holoprotein (ConA ZnCa). Ca2+ has induced large conformational changes to stabilize its hepta-coordination in the S2 site, which comprise the trans to cis isomerization of the Ala207-Asp208 peptide bond accompanied by the formation of the saccharide-binding site. The Zn2+ ligation in ConA ZnCa is similar to Mn2+, Cd2+, Co2+, or Ni2+ ligation in the S1 site, in disagreement with earlier extended x-ray absorption fine structure results that suggested a lower coordination number for Zn2+.

Selected figure(s)

Figure 1.
Fig. 1. Scheme of the S1 site and its coordination of Zn2+ in: a, metal-free ConA; b, apoZn-ConA; c, Zn-ConA; and d, ConA ZnCa.

Figure 4.
Fig. 4. Omit F[o] F[c] electron densities for the metal ions Zn2+ in the S1 site and Ca^2+ in the S2 site and their water ligands in ConA ZnCa.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (1996, 271, 16144-16150) copyright 1996.

Figures were selected by an automated process.