PDBsum entry 4wn0

Sugar binding protein

PDB id: 4wn0

Contents

Protein chain

277 a.a.

Ligands

PO4

1PE ×4

G3P

Metals

_CA ×3

Waters ×167

PDB id:

4wn0

Name:

Sugar binding protein

Title:

Xenopus laevis embryonic epidermal lectin in complex with glycerol phosphate

Structure:

Xeel protein. Chain: a. Fragment: carbohydrate-binding domain. Engineered: yes

Source:

Xenopus laevis. African clawed frog. Organism_taxid: 8355. Gene: xeel. Expressed in: trichoplusia ni. Expression_system_taxid: 7111.

Resolution:

2.20Å R-factor: 0.152 R-free: 0.169

Authors:

K.Wangkanont,L.L.Kiessling,K.T.Forest

Key ref:

K.Wangkanont et al. (2016). Structures of Xenopus Embryonic Epidermal Lectin Reveal a Conserved Mechanism of Microbial Glycan Recognition. J Biol Chem, 291, 5596-5610. PubMed id: 26755729 DOI: 10.1074/jbc.M115.709212

Date:

10-Oct-14 Release date: 20-Jan-16

Protein chain

Q5PPM0  (ITLN1_XENLA) -  Intelectin-1 from Xenopus laevis

Seq: 339 a.a.

Struc: 277 a.a.

DOI no: 10.1074/jbc.M115.709212

J Biol Chem 291:5596-5610 (2016)

PubMed id: 26755729

Structures of Xenopus Embryonic Epidermal Lectin Reveal a Conserved Mechanism of Microbial Glycan Recognition.

K.Wangkanont, D.A.Wesener, J.A.Vidani, L.L.Kiessling, K.T.Forest.

ABSTRACT

Intelectins (X-type lectins), broadly distributed throughout chordates, have been implicated in innate immunity. Xenopus laevis embryonic epidermal lectin (XEEL), an intelectin secreted into environmental water by the X. laevis embryo, is postulated to function as a defense against microbes. XEEL is homologous (64% identical) to human intelectin-1 (hIntL-1), which is also implicated in innate immune defense. We showed previously that hIntL-1 binds microbial glycans bearing exocyclic vicinal diol groups. It is unknown whether XEEL has the same ligand specificity. Also unclear is whether XEEL and hIntL-1 have similar quaternary structures, as XEEL lacks the corresponding cysteine residues in hIntL-1 that stabilize the disulfide-linked trimer. These observations prompted us to further characterize XEEL. We found that hIntL-1 and XEEL have similar structural features. Even without the corresponding intermolecular disulfide bonds present in hIntL-1, the carbohydrate recognition domain of XEEL (XEELCRD) forms a stable trimer in solution. The structure of XEELCRD in complex with d-glycerol-1-phosphate, a residue present in microbe-specific glycans, indicated that the exocyclic vicinal diol coordinates to a protein-bound calcium ion. This ligand-binding mode is conserved between XEEL and hIntL-1. The domain architecture of full-length XEEL is reminiscent of a barbell, with two sets of three glycan-binding sites oriented in opposite directions. This orientation is consistent with our observation that XEEL can promote the agglutination of specific serotypes of Streptococcus pneumoniae. These data support a role for XEEL in innate immunity, and they highlight structural and functional conservation of X-type lectins among chordates.