Permuteins of interleukin 1{beta}--a simplified approach for the construction of permutated proteins having new termini

A technique for the rapid and simple generation of permutatedversions of the interleukin-1ß (IL-1ß) geneis described. In this method, the human IL-1ß cDNAis twice amplified by the polymerase chain reaction (PCR) andthe resulting DNA fragments are ligated in tandem. Between thetwo genes, the DNA sequence encodes a short four amino acidloop to link the native N- and C-terminal ends of the IL-1ßprotein. By using PCR amplification from this starting template,a new version of the IL-1ß cDNA was obtained thatencodes a permutated form of the IL-1ß protein wherethe new N- and C-terminal amino acids correspond to residues65 and 64 of the native IL-1ß sequence, respectively.The name ‘permutein’ is proposed to describe proteinsgenerated by this technology. The molecular profile (IL-1 receptorbinding, biologic activity and solution properties) of the IL-1permutein produced by this technology, permutein 65/64, is shownto be identical to that of native IL-1ß The approachshould be useful to define further the structural features ofthis protein that are important for its function.     

Macrophage scavenger receptor confers an adherent phenotype to cells in culture

Chromosomal imprints in the broadest sense can arise in somatic as well as germline cells. They can be imposed through the modification of chromosomal proteins or by the modification of chromosomal DNA, and they typically effect the expression of nearby genes. Modification enzymes--such as histone deacetylases and cytosine methyltransferases, as well as chromatin components--are known to play this role in animals and many of these same enzymes and components have been found in plants. Transposable elements are subject to chromosomal imprinting and may play a fundamental role in this process in plant and other eukaryotic genomes.     

Multivalent ligand-receptor binding interactions in the fibroblast growth factor system produce a cooperative growth factor and heparin mechanism for receptor dimerization

The binding interactions for the three primary reactants of the fibroblast growth factor (FGF) system, basic FGF (bFGF), an FGF receptor, FGFR1, and the cofactor heparin/heparan sulfate (HS), were explored by isothermal titrating calorimetry, ultracentrifugation, and molecular modeling. The binding reactions were first dissected into three binary reactions: (1) FGFR1 + bFGF<==>FGFR1/bFGF, K1 = 41 (+/- 12) nM; (2) FGFR1 + HS<==>FGFR1/HS, K2 = 104 (+/- 17) microM; and (3) bFGF + HS<==>bFGF/HS, K3 = 470 (+/- 20) nM, where HS = low MW heparin, approximately 3 kDa. The first, binding of bFGF to FGFR1 in the absence of HS, was found to be a simple binary binding reaction that is enthalpy dominated and characterized by a single equilibrium constant, K1. The conditional reactions of bFGF and FGFR1 in the presence of heparin were then examined under conditions that saturate only the bFGF heparin site (1.5 equiv of HS/bFGF) or saturate the HS binding sites of both bFGF and FGFR1 (1.0 mM HS). Both 3-and 5-kDa low MW heparins increased the affinity for FGFR1 binding to bFGF by approximately 10-fold (Kd = 4.9 +/- 2.0 nM), relative to the reaction with no HS. In addition, HS, at a minimum of 1.5 equiv/bFGF, induced a second FGFR1 molecule to bind to another lower affinity secondary site on bFGF (K4 = 1.9 +/- 0.7 microM) in an entropy-dominated reaction to yield a quaternary complex containing two FGFR1, one bFGF, and at least one HS. Molecular weight estimates by analytical ultracentrifugation of such fully bound complexes were consistent with this proposed composition. To understand these binding reactions in terms of structural components of FGFR1, a three-dimensional model of FGFR1 was constructed using segment match modeling. Electrostatic potential calculations confirmed that an elongated cluster, approximately 15 x 35 A, of nine cationic residues focused positive potential (+2kBT) to the solvent-exposed beta-sheet A, B, E, C' surface of the D(II) domain model, strongly implicating this locus as the HS binding region of FGFR1. Structural models for HS binding to FGFR1, and HS binding to bFGF, were built individually and then assembled to juxtapose adjacent binding sites for receptor and HS on bFGF, against matching proposed growth factor and HS binding sites on FGFR1. The calorimetric binding results and the molecular modeling exercises suggest that bFGF and HS participate in a concerted bridge mechanism for the dimerization of FGFR1 in vitro and presumably for mitogenic signal transduction in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)     

Mathematical Software in Basic Dint: Data Integration

With this software package, a PC, and a modest grasp of Basic, users can perform and plot integrals over experimental data.