PDBsum entry 1r14

Sugar binding protein

PDB id: 1r14

Contents

Protein chain

145 a.a. *

Ligands

MES

Metals

_SM ×2

Waters ×6

* Residue conservation analysis

PDB id:

1r14

Name:

Sugar binding protein

Title:

Carbohydrate recognition and neck domains of surfactant protein a (sp- a) containing samarium

Structure:

Pulmonary surfactant-associated protein a. Chain: a. Fragment: crd and neck domains. Synonym: sp-a, psp-a, psap. Engineered: yes. Mutation: yes

Source:

Rattus norvegicus. Norway rat. Organism_taxid: 10116. Gene: sftpa1 or sftpa or sftp1 or sftp-1. Expressed in: trichoplusia. Expression_system_taxid: 7110.

Biol. unit:

Trimer (from PDB file)

Resolution:

2.50Å R-factor: 0.222 R-free: 0.247

Authors:

J.F.Head,T.R.Mealy,F.X.Mccormack,B.A.Seaton

Key ref:

J.F.Head et al. (2003). Crystal structure of trimeric carbohydrate recognition and neck domains of surfactant protein A. J Biol Chem, 278, 43254-43260. PubMed id: 12913002 DOI: 10.1074/jbc.M305628200

Date:

23-Sep-03 Release date: 11-Nov-03

Protein chain

P08427  (SFTPA_RAT) -  Pulmonary surfactant-associated protein A from Rattus norvegicus

Seq: 248 a.a.

Struc: 145 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1074/jbc.M305628200

J Biol Chem 278:43254-43260 (2003)

PubMed id: 12913002

Crystal structure of trimeric carbohydrate recognition and neck domains of surfactant protein A.

J.F.Head, T.R.Mealy, F.X.McCormack, B.A.Seaton.

ABSTRACT

Surfactant protein A (SP-A), one of four proteins associated with pulmonary surfactant, binds with high affinity to alveolar phospholipid membranes, positioning the protein at the first line of defense against inhaled pathogens. SP-A exhibits both calcium-dependent carbohydrate binding, a characteristic of the collectin family, and specific interactions with lipid membrane components. The crystal structure of the trimeric carbohydrate recognition domain and neck domain of SP-A was solved to 2.1-A resolution with multiwavelength anomalous dispersion phasing from samarium. Two metal binding sites were identified, one in the highly conserved lectin site and the other 8.5 A away. The interdomain carbohydrate recognition domain-neck angle is significantly less in SP-A than in the homologous collectins, surfactant protein D, and mannose-binding protein. This conformational difference may endow the SP-A trimer with a more extensive hydrophobic surface capable of binding lipophilic membrane components. The appearance of this surface suggests a putative binding region for membrane-derived SP-A ligands such as phosphatidylcholine and lipid A, the endotoxic lipid component of bacterial lipopolysaccharide that mediates the potentially lethal effects of Gram-negative bacterial infection.

Selected figure(s)

Figure 4.
FIG. 4. Samarium binding sites in SP-A. A, stereoview of the two sites in SP-A, where the bound lanthanide ions are shown as spheres and labeled 1 and 2 for primary and auxiliary, respectively. Coordination bonds appear as green dotted lines. B, comparison of primary (P) and auxiliary (A) sites by backbone superposition of CRD regions in SP-A (blue), SP-D (magenta), and MBP (yellow). SP-D and MBP coordinates are from PDB accession codes 1BO8 [PDB] and 1KWT [PDB] , respectively.

Figure 5.
FIG. 5. Electrostatic surface representations of SP-A (right) and SP-D (left). Top, calcium is present (one ion in primary site for SP-A, one ion in primary site and two ions in auxiliary sites for SP-D). Bottom, calcium is omitted from model. Positive and negative charges are represented by blue and red, respectively.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2003, 278, 43254-43260) copyright 2003.

Figures were selected by an automated process.