A Trivalent System from Vancomycin· d -Ala- d -Ala with Higher Affinity Than Avidin·Biotin

295

268

There is great demand for the development of novel therapies for ischemic cardiovascular disease, a leading cause of morbidity and mortality worldwide. We report here on the development of a completely synthetic cell-free therapy based on peptide amphiphile nanostructures designed to mimic the activity of VEGF, one of the most potent angiogenic signaling proteins. Following self-assembly of peptide amphiphiles, nanoscale filaments form that display on their surfaces a VEGF-mimetic peptide at high density. The VEGF-mimetic filaments were found to induce phosphorylation of VEGF receptors and promote proangiogenic behavior in endothelial cells, indicated by an enhancement in proliferation, survival, and migration in vitro. In a chicken embryo assay, these nanostructures elicited an angiogenic response in the host vasculature. When evaluated in a mouse hind-limb ischemia model, the nanofibers increased tissue perfusion, functional recovery, limb salvage, and treadmill endurance compared to controls, which included the VEGF-mimetic peptide alone. Immunohistological evidence also demonstrated an increase in the density of microcirculation in the ischemic hind limb, suggesting the mechanism of efficacy of this promising potential therapy is linked to the enhanced microcirculatory angiogenesis that results from treatment with these polyvalent VEGF-mimetic nanofibers.

Section: Discussionmentioning

confidence: 99%

Supramolecular nanostructures that mimic VEGF as a strategy for ischemic tissue repair

Webber

Tongers

Newcomb

et al. 2011

295

268

“…The generation of substantially higher affinity due to multivalency was elegantly demonstrated in studies using monovalent and trivalent vancomycin and D-Ala-D-Ala derivatives. These studies showed that dissociation constant of monovalent vancomycin and monovalent D-Ala-DAla is Ϸ10 Ϫ6 M, whereas the dissociation constant of the trivalent vancomycin and trivalent D-Ala-D-Ala is 10 Ϫ17 M (25). The structure presented here shows that the LC sites can bind two IC peptide fragments simultaneously.…”

mentioning

confidence: 68%

Structural and thermodynamic characterization of a cytoplasmic dynein light chain–intermediate chain complex

Williams

Roulhac²,

Roy³

et al. 2007

116

178

Cytoplasmic dynein is a microtubule-based motor protein complex that plays important roles in a wide range of fundamental cellular processes, including vesicular transport, mitosis, and cell migration. A single major form of cytoplasmic dynein associates with membranous organelles, mitotic kinetochores, the mitotic and migratory cell cortex, centrosomes, and mRNA complexes. The ability of cytoplasmic dynein to recognize such diverse forms of cargo is thought to be associated with its several accessory subunits, which reside at the base of the molecule. The dynein light chains (LCs) LC8 and TcTex1 form a subcomplex with dynein intermediate chains, and they also interact with numerous protein and ribonucleoprotein partners. This observation has led to the hypothesis that these subunits serve to tether cargo to the dynein motor. Here, we present the structure and a thermodynamic analysis of a complex of LC8 and TcTex1 associated with their intermediate chain scaffold. The intermediate chains effectively block the major putative cargo binding sites within the light chains. These data suggest that, in the dynein complex, the LCs do not bind cargo, in apparent disagreement with a role for LCs in dynein cargo binding interactions.crystal structure ͉ microtubules ͉ molecular transport ͉ protein-protein interaction

“…They have proposed that these derivatives have enhanced avidity for D-Ala-D-Lac moieties presented on bacterial cell surfaces because the interactions are effectively divalent (40). There is considerable biophysical data to support the hypothesis that lipid-substituted glycopeptides have enhanced avidity for both D-Ala-D-Ala-and D-Ala-D-Lacmodified surfaces (41), and it has also been shown that covalent dimers and trimers of vancomycin bind covalent multimers of D-Ala-D-Ala many orders of magnitude better than the monomers bind (42). Nevertheless, there is no evidence that chlorobiphenyl vancomycin derivatives kill vanA strains by dimerizing near cell surfaces and binding D-Ala-D-Lac (43,44).…”

Section: Discussionmentioning

confidence: 99%

Vancomycin analogues active against vanA-resistant strains inhibit bacterial transglycosylase without binding substrate

Chen

Walker

Sun

et al. 2003

139

147

Bacterial transglycosylases are enzymes that couple the disaccharide subunits of peptidoglycan to form long carbohydrate chains. These enzymes are the target of the pentasaccharide antibiotic moenomycin as well as the proposed target of certain glycopeptides that overcome vancomycin resistance. Because bacterial transglycosylases are difficult enzymes to study, it has not previously been possible to evaluate how moenomycin inhibits them or to determine whether glycopeptide analogues directly target them. We have identified transglycosylase assay conditions that enable kinetic analysis of inhibitors and have examined the inhibition of Escherichia coli penicillin-binding protein 1b (PBP1b) by moenomycin as well as by various glycopeptides. We report that chlorobiphenyl vancomycin analogues that are incapable of binding substrates nevertheless inhibit E. coli PBP1b, which shows that these compounds interact directly with the enzyme. These findings support the hypothesis that chlorobiphenyl vancomycin derivatives overcome vanA resistance by targeting bacterial transglycosylases. We have also found that moenomycin is not competitive with respect to the lipid II substrate of PBP1b, as has long been believed. With the development of suitable methods to evaluate bacterial transglycosylases, it is now possible to probe the mechanism of action of some potentially very important antibiotics.