Assuntos
Quimiocinas CXC/química , Quimiocinas CXC/genética , Cátions/química , Cátions/metabolismo , Quimiocina CXCL12 , Quimiocinas CXC/metabolismo , Cristalografia por Raios X , Humanos , Modelos Moleculares , Dobramento de Proteína , Estrutura Terciária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homologia Estrutural de ProteínaRESUMO
Human fibroblast growth factor receptor (FGFR) is responsible for multifunctional signaling that regulates developmental processes. The three immunoglobulin-like extracellular domains of FGFR (D1, D2, and D3) include the determinants of ligand binding and specificity for fibroblast growth factor and heparan sulfate. D1 and the D1-D2 linker with a contiguous stretch of acidic amino acids are known to be involved in auto-inhibitory regulation. In an effort to gain a better understanding of the role of D1 and the linker in FGFR regulation, we have subcloned, overexpressed, and purified the extracellular fragments, D1-D2 and D1-D3, of FGFR1 in Escherichia coli. The recombinant proteins were produced in an insoluble form and were renatured using a dropwise or on-column refolding method. In addition, D2-D3 was coexpressed with chaperones to test the possibility that the presence of chaperones might enhance refolding efficiencies. A combination of immobilized nickel and heparin affinity chromatography and size-exclusion chromatography resulted in the purification of recombinant ectodomain proteins D1-D2 and D1-D3 of high purity for structural studies.
Assuntos
Escherichia coli/metabolismo , Expressão Gênica , Receptor Tipo 1 de Fator de Crescimento de Fibroblastos/biossíntese , Receptor Tipo 1 de Fator de Crescimento de Fibroblastos/isolamento & purificação , Cromatografia de Afinidade , Escherichia coli/genética , Fator 1 de Crescimento de Fibroblastos/metabolismo , Humanos , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Ligação Proteica , Dobramento de Proteína , Receptor Tipo 1 de Fator de Crescimento de Fibroblastos/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismoRESUMO
Cephalosporin acylase (CA), a member of the N-terminal nucleophile hydrolase family, is activated through sequential primary and secondary autoproteolytic reactions with the release of a pro segment. We have determined crystal structures of four CA mutants. Two mutants are trapped after the primary cleavage, and the other two undergo secondary cleavage slowly. These structures provide a look at pro-segment conformation during activation in N-terminal nucleophile hydrolases. The highly strained helical pro segment of precursor is transformed into a relaxed loop in the intermediates, suggesting that the relaxation of structural constraints drives the primary cleavage reaction. The secondary autoproteolytic step has been proposed to be intermolecular. However, our analysis provides evidence that CA is processed in two sequential steps of intramolecular autoproteolysis involving two distinct residues in the active site, the first a serine and the second a glutamate.