7S62

Locally refined protomer structure of native-form oocyte/egg Alpha-2-Macroglobulin (A2Moo) tetramer

Summary for 7S62

• Entry DOI: 10.2210/pdb7s62/pdb
• EMDB information: 24847
• Descriptor: Alpha 2-macroglobulin, 2-acetamido-2-deoxy-beta-D-glucopyranose (2 entities in total)
• Functional Keywords: xenopus egg extract, protease inhibitor, protein binding
• Biological source: Xenopus laevis (African clawed frog)
• Total number of polymer chains: 1
• Total formula weight: 163241.35

Authors

Arimura, Y.,Funabiki, H. (deposition date: 2021-09-12, release date: 2022-01-05, Last modification date: 2022-01-19)

Primary citation

Arimura, Y.,Funabiki, H.
Structural Mechanics of the Alpha-2-Macroglobulin Transformation.
J.Mol.Biol., 434:167413-167413, 2021

PubMed Abstract: Alpha-2-Macroglobulin (A2M) is the critical pan-protease inhibitor of the innate immune system. When proteases cleave the A2M bait region, global structural transformation of the A2M tetramer is triggered to entrap the protease. The structural basis behind the cleavage-induced transformation and the protease entrapment remains unclear. Here, we report cryo-EM structures of native- and intermediate-forms of the Xenopus laevis egg A2M homolog (A2Moo or ovomacroglobulin) tetramer at 3.7-4.1 Å and 6.4 Å resolution, respectively. In the native A2Moo tetramer, two pairs of dimers arrange into a cross-like configuration with four 60 Å-wide bait-exposing grooves. Each bait in the native form threads into an aperture formed by three macroglobulin domains (MG2, MG3, MG6). The bait is released from the narrowed aperture in the induced protomer of the intermediate form. We propose that the intact bait region works as a "latch-lock" to block futile A2M transformation until its protease-mediated cleavage.

PubMed: 34942166
DOI: 10.1016/j.jmb.2021.167413

Experimental method

ELECTRON MICROSCOPY (3.65 Å)