1i4a
CRYSTAL STRUCTURE OF PHOSPHORYLATION-MIMICKING MUTANT T6D OF ANNEXIN IV
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OverviewOverview
Site-directed mutagenesis, electron microscopy, and X-ray crystallography, were used to probe the structural basis of annexin IV-induced membrane, aggregation and the inhibition of this property by protein kinase C, phosphorylation. Site-directed mutants that either mimic (Thr6Asp, T6D) or, prevent (Thr6Ala, T6A) phosphorylation of threonine 6 were produced for, these studies and compared with wild-type annexin IV. In vitro assays, showed that unmodified wild-type annexin IV and the T6A mutant, but not, PKC-phosphorylated wild-type or the T6D mutant, promote vesicle, aggregation. Electron crystallographic data of wild-type and T6D annexin, IV revealed that, similar to annexin V, the annexin IV proteins form 2D, trimer-based ordered arrays on phospholipid monolayers. Cryo-electron, microscopic images of junctions formed between lipid vesicles in the, presence of wild-type annexin IV indicated a separation distance, corresponding to the thickness of two layers of membrane-bound annexin IV., In this orientation, a single layer of WT annexin IV, attached to the, outer leaflet of one vesicle, would undergo face-to-face self-association, with the annexin layer of a second vesicle. The 2.0-A resolution crystal, structure of the T6D mutant showed that the mutation causes release of the, N-terminal tail from the protein core. This change would preclude the, face-to-face annexin self-association required to aggregate vesicles. The, data suggest that reversible complex formation through phosphorylation and, dephosphorylation could occur in vivo and play a role in the regulation of, vesicle trafficking following changes in physiological states.
About this StructureAbout this Structure
1I4A is a Single protein structure of sequence from Bos taurus with CA and SO4 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Phosphorylation mutants elucidate the mechanism of annexin IV-mediated membrane aggregation., Kaetzel MA, Mo YD, Mealy TR, Campos B, Bergsma-Schutter W, Brisson A, Dedman JR, Seaton BA, Biochemistry. 2001 Apr 3;40(13):4192-9. PMID:11300800
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