RESUMO
Nerve growth factor (NGF) is a dimeric molecule that modulates the survival, proliferation, and differentiation of nervous cells and is also known to act on cells of the immune system and endocrine system. NGFs extracted from mouse submaxillary gland and cobra venom have different immunological behaviors, yet the underlying mechanism remains unclear. Here we report the crystal structure of the NGF purified from Chinese cobra Naja naja atra (cNGF), which unexpectedly reveals a 2-tailed lipid molecule that is embedded between the two protomers of the NGF homodimer. In addition, crystallographic analysis indicated that the purified mouse NGF(mNGF) is free from lipid but can bind lysophosphatidylserine (lyso-PS) in the same pocket as cNGF. Bioassays indicated that the binding of lipid molecules to cNGF and mNGF are essential for their mast cell activation activity and abates their p75(NTR) binding capacity. Taken together, these results suggest a new mechanism for the regulation of the function of NGF.
Assuntos
Lipídeos/química , Fatores de Crescimento Neural/química , Fatores de Crescimento Neural/farmacologia , Sequência de Aminoácidos , Animais , Cristalografia por Raios X , Elapidae , Liberação de Histamina/efeitos dos fármacos , Humanos , Mastócitos/efeitos dos fármacos , Modelos Moleculares , Dados de Sequência Molecular , Fatores de Crescimento Neural/isolamento & purificação , Fatores de Crescimento Neural/metabolismo , Homologia de Sequência de Aminoácidos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Relação Estrutura-AtividadeRESUMO
Vibrio parahaemolyticus is one of important human food pathogens. Traditional diagnostic tests for V. parahaemolyticus are laborious and always present false negative results. Therefore, it is important to develop a nucleic acid-based test for quantitative detection of V. parahaemolyticus. A TaqMan PCR assay was presented for quantitative detection of V. parahaemolyticus in pure cultures and oysters. The primers and probe were designed according to the gyrase B gene (gyrB) sequence of V. parahaemolyticus strains. Amplification of DNAs from 12 bacterial strains comprising 9 genera showed that all of the strains of V. parahaemolyticus tested (n = 4) were positive and all other species of strains tested (n = 8) were negative. The results of the TaqMan PCR with raw oysters inoculated with V. parahaemolyticus were comparable to those of pure cultures. The sensitivity of the assay was 1 CFU PCR Mixture(-1) and 10 CFU PCR Mixture(-1) in pure culture and inoculated raw oyster, respectively. The correlation rate was 0.99 (gamma2 = 0.99). The assay could be completed within 1h. The Real-time PCR can be used as a rapid screening tool for the presence of V. parahaemolyticus in seafood without prior isolation and characterization of the bacteria by traditional microbiological methods.
