EFFECTS OF SULFHYDRYL REAGENTS ON BRAIN MICROTUBULE-ASSOCIATED ATPase ACTIVITY IN VITRO |
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Authors: | Margareta Wallin H Larsson A Edström |
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Institution: | Department of Zoophysiology, University of Göteborg, Fack, S-400 33 Göteborg, Sweden;Department of Zoophysiology, University of Lund, S-223 62 Lund, Sweden |
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Abstract: | Abstract— The effects of two sulfhydryl reagents, PCMBS ( p -chloromercuribenzene sulfonic acid) and NEM ( N -ethylmaleimide) on microtubule-associated Mg2+ -and Ca2+ -ATPase activity were studied in a MTP (microtubule proteins) preparation and in a MAP (microtubule-associated proteins) fraction. In the MTP preparation at pH 6.8, PCMBS stimulated the Mg2+ -ATPase activity at low concentrations and inhibited at higher, whereas the Ca2+ -ATPdse activity was only inhibited. NEM affected the activity in a similar way. At pH 8.0 PCMBS was only inhibitory. NEM showed stimulatory effects over a broader concentration range. Preincubation in the presence of ATP counteracted the stimulatory effects of both PCMBS and NEM on Mg2+ -ATPase at pH 6.8. In the MAP fraction at pH 6.8 PCMBS and NEM caused similar but less pronounced effects on the Mg2+ -and Ca2+ -ATPase. The results show that brain microtubule-associated ATPase activity is similar to dynein and myosin ATPases with respect to biphasic alteration by sulfhydryl reagents. |
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