Togawa A, Ito H, Kimura F, Shimizu H, Ohtsuka M, Shimamura F,
Yoshidome H, Katoh A, Miyazaki M.
Establishment of gemcitabine-resistant human
pancreatic cancer cells and effect of Brefeldin-A on the
resistant cell line.
Pancreas. 2003 Oct;27(3):220-4.
Howard Hughes Medical Institute, Structural
Biology Program, Memorial Sloan-Kettering Cancer Center, 1275
York Avenue, New York, NY 10021, USA.
ARF GTPases are activated by guanine nucleotide exchange factors
(GEFs) of the Sec7 family that promote the exchange of GDP for
GTP. Brefeldin A (BFA) is a fungal metabolite that binds to the
ARF1*GDP*Sec7 complex and blocks GEF activity at an early stage
of the reaction, prior to guanine nucleotide release. The
crystal structure of the ARF1*GDP*Sec7*BFA complex shows that
BFA binds at the protein-protein interface to inhibit
conformational changes in ARF1 required for Sec7 to dislodge the
GDP molecule. Based on a comparative analysis of the inhibited
complex, nucleotide-free ARF1*Sec7 and ARF1*GDP, we suggest
that, in addition to forcing nucleotide release, the ARF1-Sec7
binding energy is used to open a cavity on ARF1 to facilitate
the rearrangement of hydrophobic core residues between the GDP
and GTP conformations. Thus, the Sec7 domain may act as a dual
catalyst, facilitating both nucleotide release and
conformational switching on ARF proteins.
PMID: 14690595
|
