PDBsum entry 1jn2

Sugar binding protein

PDB id: 1jn2

Contents

Protein chain

237 a.a. *

Ligands

SFP

Metals

_CA

_MN

Waters ×51

* Residue conservation analysis

PDB id:

1jn2

Name:

Sugar binding protein

Title:

Crystal structure of meso-tetrasulphonatophenyl porphyrin complexed with concanavalin a

Structure:

Concanavalin-a. Chain: p. Fragment: unp p02866 residues 164-281, 30-148. Synonym: con a

Source:

Canavalia ensiformis. Jack bean. Organism_taxid: 3823

Biol. unit:

Tetramer (from PQS)

Resolution:

1.90Å R-factor: 0.195 R-free: 0.232

Authors:

M.Goel,D.Jain,K.J.Kaur,R.Kenoth,B.G.Maiya,M.J.Swamy,D.M.Salunke

Key ref:

M.Goel et al. (2001). Functional equality in the absence of structural similarity: an added dimension to molecular mimicry. J Biol Chem, 276, 39277-39281. PubMed id: 11504727 DOI: 10.1074/jbc.M105387200

Date:

22-Jul-01 Release date: 01-Jul-03

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.M105387200

J Biol Chem 276:39277-39281 (2001)

PubMed id: 11504727

Functional equality in the absence of structural similarity: an added dimension to molecular mimicry.

M.Goel, D.Jain, K.J.Kaur, R.Kenoth, B.G.Maiya, M.J.Swamy, D.M.Salunke.

ABSTRACT

The crystal structure of meso-tetrasulfonatophenylporphyrin complexed with concanavalin A (ConA) was determined at 1.9 A resolution. Comparison of this structure with that of ConA bound to methyl alpha-d-mannopyranoside provided direct structural evidence of molecular mimicry in the context of ligand receptor binding. The sulfonatophenyl group of meso-tetrasulfonatophenylporphyrin occupies the same binding site on ConA as that of methyl alpha-d-mannopyranoside, a natural ligand. A pair of stacked porphyrin molecules stabilizes the crystal structure by end-to-end cross-linking with ConA resulting in a network similar to that observed upon agglutination of cells by lectins. The porphyrin binds to ConA predominantly through hydrogen bonds and water-mediated interactions. The sandwiched water molecules in the complex play a cementing role, facilitating favorable binding of porphyrin. Seven of the eight hydrogen bonds observed between methyl alpha-d-mannopyranoside and ConA are mimicked by the sulfonatophenyl group of porphyrin after incorporating two water molecules. Thus, the similarity in chemical interactions was manifested in terms of functional mimicry despite the obvious structural dissimilarity between the sugar and the porphyrin.

Selected figure(s)

Figure 2.
Fig. 2. The stereo view of the molecular conformation of H[2]TPPS in the asymmetric unit of the crystals of the H[2]TPPS·ConA complex. A, the F[o] F[c] map in the ligand-binding site on ConA, scaled at 3.2 , showing half of the H[2]TPPS molecule corresponding to the asymmetric unit. The porphyrin model has been built into the map (thick black lines). The water molecules in the region have also been shown as black spheres. The surrounding ConA residues are shown as thin gray lines. B, a stereo view of the porphyrin conformation as it appears in complex with ConA molecule. The non-carbon atoms belonging to one asymmetric unit are labeled.

Figure 3.
Fig. 3. A stereo view of the unique self-stacking arrangement of the porphyrin molecules in the H[2]TPPS·ConA complex. The stacked porphyrins are slightly staggered to prevent steric clashes between the side groups (thick blue sticks). Two stacked porphyrins are surrounded by four independent monomers of ConA. The porphyrin in the asymmetric unit interacts with only six amino acid residues of ConA. The ConA residues (sticks) and water molecules (spheres) of one asymmetric unit involved in interactions with porphyrin are shown in the same color.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2001, 276, 39277-39281) copyright 2001.

Figures were selected by an automated process.