Mastoparan activation of G proteins and NDPK.

Cornelius Krasel krasel at
Wed Feb 23 14:07:42 EST 1994

Jon Nakamoto (jnakamot at wrote:

: Calling all G-protein researchers [there must be thousands out there
: somewhere!])

I'm listening :-)

: Koch G; Mohr C; Just I; Aktories K.
:        Posttranslational isoprenylation of rho protein is a
: prerequisite for its interaction with mastoparan and other amphiphilic
: agents.
:      Biochemical and Biophysical Research Communications, 1992 Jul 15,
:      186(1):448-54.
:  Abstract: The amphiphilic agents melittin, compound 48/80 and
: mastoparan inhibit ADP-ribosylation of porcine brain rho protein by
: Clostridium botulinum exoenzyme C3. However, ADP-ribosylation of
: recombinant rhoA expressed in E.coli was not inhibited by these agents.
: Accordingly, steady state GTP hydrolysis by recombinant rhoA was not
: stimulated by mastoparan, whereas GTP hydrolysis by porcine brain rho
: was stimulated 2.5-fold in the presence ofthis wasp venom. After
: microinjection of recombinant rhoA into Xenopuslaevis oocytes the
: inhibitory effect of mastoparan on C3 ADP-ribosylation was restored.
: The data suggest that the amphiphilic agents tested are only active at
: the posttranslationally processed form of rho and that they exert their
: effects via the C-terminal end.

I'm not sure about the author's conclusion. Wouldn't the experiments suggest
that ADP ribosylation by the toxin (I'm more familiar with pertussis
toxin, though) is only possible if the rho protein is targeted to the
membrane by its myristoylated C-terminus? In terms of structural biology
this seems more likely to me.


/* Cornelius Krasel, Abt. Lohse, Genzentrum, D-82152 Martinsried, Germany */
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