posted on 2024-01-19, 01:05authored byAzadeh Alavizargar, Maximilian Gass, Michael P. Krahn, Andreas Heuer
Intrinsically disordered
regions of proteins are responsible for
many biological processes such as in the case of liver kinase B1 (LKB1)a
serine/threonine kinase relevant for cell proliferation and cell polarity.
LKB1 becomes fully activated upon recruitment to the plasma membrane
by binding of its disordered C-terminal polybasic motif consisting
of eight lysines/arginines to phospholipids. Here, we present extensive
molecular dynamics (MD) simulations of the polybasic motif interacting
with a model membrane composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleyl phosphatidic
acid (PA) and cell culture experiments. Protein–membrane binding
effects are due to the electrostatic interactions between the polybasic
amino acids and PAs. For significant binding, the first three lysines
turn out to be dispensable, which was also recapitulated in cell culture
using transfected GFP-LKB1 variants. LKB1–membrane binding
results in nonmonotonous changes in the structure of the protein as
well as the membrane, in particular, accumulation of PAs and reduced
thickness at the protein–membrane contact area. The protein–lipid
binding turns out to be highly dynamic due to an interplay of PA–PA
repulsion and protein–PA attraction. The thermodynamics of
this interplay is captured by a statistical fluctuation model, which
allows the estimation of both energies. Quantification of the significance
of each polar amino acid in the polybasic provides detailed insights
into the molecular mechanism of protein–membrane binding of
LKB1. These results can likely be transferred to other proteins, which
interact by intrinsically disordered polybasic regions with anionic
membranes.