Decoding of sorting signals by coatomer through a GTPase switch in thE COPI coat complex

Article Abstract:

The coatomer subunits of the COPI protein complex respond differently to different signals. This may explain how the complex segregates different cargo proteins during protein transport between cell organelles.

Biological transport, Active, Active biological transport, Cellular signal transduction

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Structural basis for activation of ARF GTPase: Mechanisms of guanine nucleotide exchange and GTP-myristoyl switching

Article Abstract:

Guanine nucleotide exchange factors (GEFs) positively control GTPases by promoting GDP exchange for GTP, leading to an active conformation, interacting specifically with downstream effectors. The crystal structure of the Sec7 domain GEF bound to ARF1 GTPase was determined at 2.8 A resolution. The interaction of the Sec7 domain, binding to the switch regions of ARF1 leaves the purine-binding site intact, but perturbs the Mg(super2+) and phosphate groups, promoting the dissociation of guanine nucleotides.

Observations, Guanine

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Structural and functional analysis of the ARF1-ARFGAP complex reveals a role for coatomer in GTP hydrolysis

Article Abstract:

A study was conducted to determine the crystal structure and functions of a complex of human ARF1 and rat ARF-specific GTPase-activating protein (ARFGAP) at 1.95 A resolution. Results reveal that the ARFGAP residues do not reside within the 15 A of the GTPase active site. Hence, ARFGAP can only speed up GTP hydrolysis by stabilizing the switch 2 region but cannot generate catalytic arginine or other amino acid side chains.

Hydrolysis

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