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Zinc Ions Stabilise the Association of Basic Protein with Brain Myelin Membranes
Author(s) -
Earl Christopher,
Chantry Andrew,
Mohammad Nazar,
Glynn Paul
Publication year - 1988
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1988.tb01803.x
Subject(s) - chemistry , zinc , myelin basic protein , membrane , myelin , calcium , dissociation (chemistry) , biochemistry , chromatography , biology , organic chemistry , neuroscience , central nervous system
Myelin basic protein (MBP) dissociated from brain myelin membranes when they were incubated (37°C; pH 7.4) at physiological ionic strength. Zinc ions inhibited, and calcium promoted, this process. Protease activity in the membrane preparations cleaved the dissociated MBP into both small (<4 kilodaltons) and large (>8 kilodaltons) fragments. The latter were detected, together with intact MBP, by gel electrophoresis of incubation media. Zinc ions appeared to act in two distinct processes. In the presence or absence of added CaC1 2 , zinc ions in the range 0.1–1 m M inhibited MBP‐membrane dissociation. This process was relatively insensitive to heat and Zn 2+ could be substituted by either copper (II) or cobalt (II) ions. A second effect was evident only in the presence of added calcium ions, when lower concentrations of Zn 2+ (<0.1 m M ) inhibited MBP‐membrane dissociation and the accumulation of intact MBP in incubation media. This process was heat sensitive and only copper (II), but not cobalt (II), ions could replace Zn 2+ . To determine whether endogenous zinc in myelin membranes is bound to MBP, preparations were solubilised in buffers containing Triton X‐100/2 m M CaCl 2 and subjected to gel filtration. Endogenous zinc, as indicated by a dithizone‐binding method, eluted with fractions containing both MBP and proteolipid protein (PLP). Thus, one means whereby zinc stabilises association of MBP with brain myelin membranes may be by promoting its binding to PLP.