tailieunhanh - Báo cáo khoa học: EspB from enterohaemorrhagic Escherichia coli is a natively partially folded protein

The structural properties of EspB, a virulence factor of theEscherichia coli O157 type III secretion system, were characterized. Far-UV and near-UV CD spectra, recorded between pH and pH , show that the protein assumesa-helical structures and that some tyrosine tertiary contacts may exist. All tyrosine side-chains are exposed to water, as determined by acryl-amide fluorescence quenching spectroscopy. | iFEBS Journal EspB from enterohaemorrhagic Escherichia coli is a natively partially folded protein Daizo Hamada1 Tomoaki Kato1 2 Takahisa Ikegami3 Kayo N. Suzuki1 Makoto Hayashi2 Yoshikatsu Murooka2 Takeshi Honda4 and Itaru Yanagihara1 1 Department of DevelopmentalInfectious Diseases Research Institute Osaka MedicalCenter for Maternaland Child Health Japan 2 Department of Biotechnology Graduate Schoolof Engineering Osaka University Japan 3 Laboratory of StructuralProteomics Institute for Protein Research Osaka University Japan 4 Department of BacterialInfections Research Institute for MicrobialDiseases Osaka University Japan Keywords circular dichroism natively partially folded proteins nuclear magnetic resonance fluorescence quenching multiangle laser light scattering Correspondence I. Yanagihara Department of Developmental Infectious Diseases Research Institute Osaka MedicalCenter for Maternaland Child Health 840 Murodo Izumi Osaka 594-1011 Japan Fax 81 725 57 3021 Tel 81 725 56 1220 ext. 5302 E-mail itaruy@ Received 20 August 2004 revised 17 November 2004 accepted 2 December 2004 doi The structural properties of EspB a virulence factor of the Escherichia coli O157 type III secretion system were characterized. Far-UV and near-UV CD spectra recorded between pH and pH show that the protein assumes a-helical structures and that some tyrosine tertiary contacts may exist. All tyrosine side-chains are exposed to water as determined by acrylamide fluorescence quenching spectroscopy. An increase in the fluorescence intensity of 8-anilinonaphthalene-1-sulfonate was observed at pH in the presence of EspB whereas no such increase in fluorescence was observed at pH . These data suggest the formation of a molten globule state at pH . Destabilization of EspB at low pH was shown by urea-unfolding transitions monitored by far-UV CD spectroscopy. The result from a sedimentation equilibrium study indicated that .