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W F Degrado

Publications and source records attributed to W F Degrado.

6 recordsLinked to original sources
PubMed2004

Structural basis for integrin alphaIIbbeta3 clustering.

We have expressed two proteins that correspond to the transmembrane and cytoplasmic domains of integrin alphaIIb and beta3 subunits. Characterization of these proteins, dispersed in anionic and zwitterionic micelles, revealed that, rather than interacting with each other, the two proteins associated into homodimers and homotrimers respectively. Moreover, studies using the TOXCAT assay system confirmed that the alphaIIb and beta3 transmembrane domains can self-associate in biological cell membranes. Transmembrane domain-mediated homo-oligomerization provides a plausible structural basis for integrin clustering and could promote integrin activation as well. Indeed, replacing specific residues in the transmembrane helix of either alphaIIb or beta3 with an asparagine residue resulted in a facilitated homo-oligomerization of the mutated transmembrane helix, promoted the formation of integrin clusters on the cell surface and shifted alphaIIbbeta3 to its activated state. Thus these studies support the hypothesis that the transmembrane domains play a vital role in the function and regulation of alphaIIbbeta3.

Amino Acid Motifs↗
PubMed2001

Proton and metal ion-dependent assembly of a model diiron protein.

DF1 is a small, idealized model for carboxylate-bridged diiron proteins. This protein was designed to form a dimeric four-helix bundle with a dimetal ion-binding site near the center of the structure, and its crystal structure has confirmed that it adopts the intended conformation. However, the protein showed limited solubility in aqueous buffer, and access to its active site was blocked by two hydrophobic side chains. The sequence of DF1 has now been modified to provide a very soluble protein (DF2) that binds metal ions in a rapid and reversible manner. Furthermore, the DF2 protein shows significant ferroxidase activity, suggesting that its dimetal center is accessible to oxygen. The affinity of DF2 for various first-row divalent cations deviates from the Irving-Willliams series, suggesting that its structure imparts significant geometric preferences on the metal ion-binding site. Furthermore, in the absence of metal ions, the protein folds into a dimer with concomitant binding of two protons. The uptake of two protons is expected if the structure of the apo-protein is similar to that of the crystal structure of dizinc DF1. Thus, this result suggests that the active site of DF2 is retained in the absence of metal ions.

Amino Acid Sequence↗
PubMed1997

The crystal structure of the designed trimeric coiled coil coil-VaLd: implications for engineering crystals and supramolecular assemblies.

The three-dimensional structure of the 29-residue designed coiled coil having the amino acid sequence acetyl-E VEALEKK VAALESK VQALEKK VEALEHG-amide has been determined and refined to a crystallographic R-factor of 21.4% for all data from 10-A to 2.1-A resolution. This molecule is called coil-VaLd because it contains valine in the a heptad positions and leucine in the d heptad positions. In the trigonal crystal, three molecules, related by a crystallographic threefold axis, form a parallel three-helix bundle. The bundles are stacked head-to-tail to form a continuous coiled coil along the c-direction of the crystal. The contacts among the three helices within the coiled coil are mainly hydrophobic: four layers of valine residues alternate with four layers of leucine residues to form the core of the bundle. In contrast, mostly hydrophilic contacts mediate the interaction between trimers: here a total of two direct protein--protein hydrogen bonds are found. Based on the structure, we propose a scheme for designing crystals of peptides containing continuous two-, three-, and four-stranded coiled coils.

Amino Acid Sequence↗
PubMed1992

Peptide models for the membrane destabilizing actions of viral fusion proteins.

The fusion of enveloped viruses to target membranes is promoted by certain viral fusion proteins. However, many other proteins and peptides stabilize bilayer membranes and inhibit membrane fusion. We have evaluated some characteristics of the interaction of peptides that are models of segments of measles and influenza fusion proteins with membranes. Our results indicate that these models of the fusogenic domains of viral fusion proteins promote conversion of model membrane bilayers to nonbilayer phases. This is opposite to the effects of peptides and proteins that inhibit viral fusion. A peptide model for the fusion segment of the HA protein of influenza increased membrane leakage as well as promoted the formation of nonbilayer phases upon acidification from pH 7-5. We analyze the gross conformational features of the peptides, and speculate on how these conformational features relate to the structures of the intact proteins and to their role in promoting membrane fusion.

Amino Acid Sequence↗