Open AccessSolution structures and biophysical analysis of full-length group A PAKs reveal they are monomeric and auto-inhibited in cis
Author(s) -
F.J. Sorrell,
Lena Marie Kilian,
J.M. Elkins
Publication year - 2019
Publication title -
biochemical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.706
H-Index - 265
eISSN - 1470-8728
pISSN - 0264-6021
DOI - 10.1042/bcj20180867
Subject(s) - pak1 , phosphorylation , cdc42 , kinase , gtpase , monomer , biophysics , chemistry , stereochemistry , crystallography , biochemistry , biology , polymer , organic chemistry
The group A p21-activated kinases (PAKs) exist in an auto-inhibited form until activated by GTPase binding and auto-phosphorylation. In the auto-inhibited form, a regulatory domain binds to the kinase domain (KD) blocking the binding of substrates, and CDC42 or Rac binding to the regulatory domain relieves this auto-inhibition allowing auto-phosphorylation on the KD activation loop. We have determined the crystal structure of the PAK3 catalytic domain and by small angle X-ray scattering, the solution-phase structures of full-length inactive PAK1 and PAK3. The structures reveal a compact but elongated molecular shape that demonstrates that, together with multiple independent biophysical measurements and in contrast with previous assumptions, group A PAKs are monomeric both before and after activation, consistent with an activation mechanism of cis -auto-inhibition and initial cis -auto-phosphorylation, followed by transient dimerisation to allow trans -auto-phosphorylation for full activation, yielding a monomeric active PAK protein.