PDBsum entry 2ocw

Immune system

PDB id

2ocw

Contents

			Protein chain

					585 a.a.*

* C-alpha coords only

References listed in PDB file

Key reference

Title

Solution structure of human secretory component and implications for biological function.

Authors

A.Bonner, C.Perrier, B.Corthésy, S.J.Perkins.

Ref.

J Biol Chem, 2007, 282, 16969-16980. [DOI no: 10.1074/jbc.M701281200]

PubMed id

17428798

Abstract

Secretory component (SC) in association with polymeric IgA (pIgA) forms secretory IgA, the major antibody active at mucosal surfaces. SC also exists in the free form, with innate-like neutralizing properties against pathogens. Free SC consists of five glycosylated variable (V)-type Ig domains (D1-D5), whose structure was determined by x-ray and neutron scattering, ultracentrifugation, and modeling. With a radius of gyration of 3.53-3.63 nm, a length of 12.5 nm, and a sedimentation coefficient of 4.0 S, SC possesses an unexpected compact structure. Constrained scattering modeling based on up to 13,000 trial models shows that SC adopts a J-shaped structure in which D4 and D5 are folded back against D2 and D3. The seven glycosylation sites are located on one side of SC, leaving known IgA-binding motifs free to interact with pIgA. This work represents the first analysis of the three-dimensional structure of full-length free SC and paves the way to a better understanding of the association between SC and its potential ligands, i.e. pIgA and pathogenic-associated motifs.



	Figure 3. FIGURE 3. Distance distribution functions P(r) for SC, D1–D3, and D4–D5. M represents the most frequent distance, and L represents the maximum dimension (Table 1). A and B, the x-ray and neutron P(r) curves for SC. C and D, the x-ray P(r) curves for D1–D3 and D4–D5.		Figure 5. FIGURE 5. Sedimentation velocity fits for SC, D1–D3, and D4–D5 by SEDFIT. The boundary fits are shown to the left and the c(s) plots are shown to the right. A and E, SC at 1.24 mg/ml and 30,000 rpm, showing every 5th boundary of the first 100; B and F, D1–D3 at 1.6 mg/ml and 42,000 rpm, showing every 16th boundary of 500; C and G, D4–D5 at 0.40 mg/ml and 42,000 rpm, showing every 5th boundary of the first 55; and D and H, cleaved SC at 0.31 mg/ml and 42,000 rpm, showing every 5th boundary of the first 110.

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