IQGAP1 has emerged as a key component in the regulation of cytoskeleton dynamics during cell migration, maintenance of adherens junctions, microbial pathogenesis and intracellular trafficking. IQGAP1 is known to localize to the protruding edge of lamellipodia in a variety of cell types and interact with regulators of actin dynamics. Here, we provide evidence suggesting a novel role of IQGAP1 in cell motility through cell edge retraction. In some of the cell lines examined, IQGAP1 was markedly separated from WAVE localization suggesting IQGAP1 may localize to retracting edges. B16F10 mouse melanoma cells exhibited the most restricted separation in which the appearance of GFP-IQGAP1 correlated with cell edge retraction velocity and the disappearance of mCherry-Arp3. These results demonstrate that in some cell types IQGAP1 may function to promote cell retraction not lamellipodium edge protrusion. In addition, we examined co-localization of IQGAP1 with adhesion site markers, myosin IIA, calmodulin and IQGAP2. In areas rich in IQGAP1 there was decreased immunofluorescence staining of vinculin, paxillin and phosphorylated-tyrosine indicating adhesion site disassembly. Interestingly, calmodulin, but not myosin IIA or IQGAP2, co-localized with IQGAP1 in areas of cell retraction. Overall these results suggest a new role of IQGAP1, distinct form IQGAP2, in cell migration through up regulation of contractility and downregulation of adhesion sites potentially through calmodulin interaction.

No abstract

Phenyl bis(2‐pyridyl)phosphine [PhP(2‐py)2] and its silver nitrate complex of formula [Ag2(μ‐(PhP(2‐py)2)2(NO3)2] (1) were synthesized and characterized by elemental analysis, IR spectroscopy, single‐crystal X‐ray diffraction, and computational studies. The silver(I) complex 1 with a 1:1 metal‐ligand molar ratio is dinuclear cluster with silver atoms in same environments. Biological studies, carried out in vitro against wide range of gram positive and gram negative bacteria, have shown that the free [PhP(2‐py)2] ligand and its silver complex show distinct differences in the biological properties.

No abstract

The link between cofactor binding and protein activity is well-established. However, how cofactor interactions modulate folding of large proteins remains unknown. We use optical tweezers, clustering and global fitting to dissect the folding mechanism of Drosophila cryptochrome (dCRY), a 542-residue protein that binds FAD, one of the most chemically and structurally complex cofactors in nature. We show that the first dCRY parts to fold are independent of FAD, but later steps are FAD-driven as the remaining polypeptide folds around the cofactor. FAD binds to largely unfolded intermediates, yet with association kinetics above the diffusion-limit. Interestingly, not all FAD moieties are required for folding: whereas the isoalloxazine ring linked to ribitol and one phosphate is sufficient to drive complete folding, the adenosine ring with phosphates only leads to partial folding. Lastly, we propose a dCRY folding model where regions that undergo conformational transitions during signal transduction are the last to fold.