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  • Title: Protease activation of alpha2-macroglobulin modulates a chaperone-like action with broad specificity.
    Author: French K, Yerbury JJ, Wilson MR.
    Journal: Biochemistry; 2008 Jan 29; 47(4):1176-85. PubMed ID: 18171086.
    Abstract:
    Alpha2-macroglobulin (alpha2M) is a major human blood glycoprotein best known for its ability to inhibit a broad spectrum of proteases by a unique trapping method. This action induces an "activated" conformation of alpha2M with an exposed binding site for the low-density lipoprotein receptor, facilitating clearance of alpha2M/protease complexes from the body. This report establishes that protease activation also modulates a potent chaperone-like action of alpha2M that has broad specificity for proteins partly unfolded as a result of heat or oxidative stress. Protease-mediated activation of alpha2M abolishes its chaperone-like activity. However, native alpha2M is able to form soluble complexes with stressed proteins and then subsequently become activated by interacting with a protease, providing a potential mechanism for the in vivo clearance of alpha2M/stressed protein/protease complexes. We propose that alpha2M is a newly discovered and unique member of a small group of abundant extracellular proteins with chaperone properties that patrol extracellular spaces for unfolded/misfolded proteins and facilitate their disposal.
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