ULTRASTRUCTURAL AND ANTIPROTEINASE ACTIVITY MODIFICATIONS OF HUMAN ALPHA-2-MACROGLOBULIN INDUCED BY ZINC AND OTHER DIVALENT-CATIONS

  • 1 December 1986
    • journal article
    • research article
    • Vol. 42  (2) , 359-364
Abstract
Native tetrameric .alpha.2-macroglobulin molecules (.alpha.2M) can be converted into a population of dimers by incubation with various divalent cations such as Zn, Cd, Mg, Cu, Ni, Co. This dissociation is completed within 30 min at 37.degree. C. These dimers have a characteristic shape and a size of about 16 .times. 8 nm, and appear to be the half of the native .alpha.2M molecule which has a clear tetrameric structure as seen in the electron microscope. At room temperature or below, dimers obtained with 5 to 100 mM Zn2+ can reassociate in long linear polymers which display a regular chain-like arrangement and a helical periodicity. The structural characteristics of this polymer are described. The trypsin inhibitory capacity of Zn2+-treated .alpha.2M has been studied in an attempt to correlate its Zn2+-induced conformational changes with its functional modifications.