The PH domain in the ArfGAP ASAP1 drives catalytic activation through an unprecedented allosteric mechanism.

ASAP1 is a multidomain Arf GTPase-activating protein (ArfGAP) that catalyzes GTP hydrolysis on the small GTPase Arf1 and is implicated in cancer progression. The PH domain of ASAP1 enhances its activity greater than 7 orders of magnitude but the underlying mechanisms remain poorly understood. Here, we combined Nuclear Magnetic Resonance (NMR), Molecular Dynamic (MD) simulations and mathematical modeling of functional data to build a comprehensive structural-mechanistic model of the complex of Arf1 and the ASAP1 PH domain on a membrane surface.

Point mutations in Arf1 reveal cooperative effects of the N-terminal extension and myristate for GTPase-activating protein catalytic activity.

The ADP-ribosylation factors (Arfs) constitute a family of small GTPases within the Ras superfamily, with a distinguishing structural feature of a hypervariable N-terminal extension of the G domain modified with myristate. Arf proteins, including Arf1, have roles in membrane trafficking and cytoskeletal dynamics. While screening for Arf1:small molecule co-crystals, we serendipitously solved the crystal structure of the non-myristoylated engineered mutation [L8K]Arf1 in complex with a GDP analogue.

Genome-wide analysis of host responses to the Pseudomonas aeruginosa type III secretion system yields synergistic effects.

The type III secretion system (TTSS) is a dedicated bacterial pathogen protein targeting system that directly affects host cell signalling and response pathways. Our goal was to identify host responses to the Pseudomonas aeruginosa effectors, introduced into target cells utilizing the TTSS. We carried out expression profiling of a human lung pneumocyte cell line A549 exposed to isogenic mutants of P.