1s4y

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spinqualitylabelsall models 1s4y, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of the activin/actrIIb extracellular domain

Overview

A new crystal structure of activin in complex with the extracellular domain of its type II receptor (ActRIIb-ECD) shows that the ligand exhibits an unexpected flexibility. The motion in the activin dimer disrupts its type I receptor interface, which may account for the disparity in its affinity for type I versus type II receptors. We have measured the affinities of activin and its antagonist inhibin for ActRIIb-ECD and found that the affinity of the 2-fold symmetric homodimer activin for ActRIIb-ECD depends on the availability of two spatially coupled ActRIIb-ECD molecules, whereas the affinity of the heterodimer inhibin does not. Our results indicate that activin's affinity for its two receptor types is greatly influenced by their membrane-restricted setting. We propose that activin affinity is modulated by the ligand flexibility and that cooperativity is achieved by binding to two ActRII chains that immobilize activin in a type I binding-competent orientation.

About this Structure

1S4Y is a Protein complex structure of sequences from Homo sapiens and Mus musculus. Active as Non-specific serine/threonine protein kinase, with EC number 2.7.11.1 Full crystallographic information is available from OCA.

Reference

A flexible activin explains the membrane-dependent cooperative assembly of TGF-beta family receptors., Greenwald J, Vega ME, Allendorph GP, Fischer WH, Vale W, Choe S, Mol Cell. 2004 Aug 13;15(3):485-9. PMID:15304227

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