Journal of Cell Science 115, e601-e601 (2002)
© 2002 The Company of Biologists Limited
The PX domain
The wide-ranging cellular effects of phosphoinositides are mediated through
their interaction with proteins containing lipid-binding modules such as
pleckstrin homology and FYVE domains. Recent work has revealed that the PX
domain a domain first identified in NADPH oxidase subunits several
years ago is also a phosphoinositide-binding module. On p. 1099, Chris
Ellson and co-workers discuss studies that are shedding light on the structure
and function of this domain, which in most cases is specific for
PtdIns(3)P. NMR and X-ray crystallography have revealed that the PX
domain has a novel `wedge-like' fold in which one face forms the
phosphoinositide-binding pocket; these studies are also beginning to establish
the residues that determine ligand binding specificity. The domain is most
common in proteins involved in membrane trafficking for example, the
t-SNARE Vam7p and sorting nexins. It appears to target these proteins to
PtdIns(3)P-rich membranes. The latter include endosomes and vacuoles,
in which PtdIns(3)P levels do not vary, as well as phagosomes, in
which PtdIns(3)P levels are regulated by external stimuli.