SECONDARY STRUCTURE OF THE IIB DOMAIN OF THE ESCHERICHIA-COLI MANNOSETRANSPORTER, A NEW FOLD IN THE CLASS OF ALPHA BETA TWISTED OPEN-SHEETSTRUCTURES/

The mannose transporter of the Escherichia coli bacterial phosphotrans ferase system consists of three subunits: IIAB, IIC and IID. IIAB(Man) transfers phosphoryl groups to the transported substrate via phosphoh istidine intermediates. Its IIB domain was overexpressed and isotopica lly labelled with C-13, N-15 and H-2. Heteronuclear 3D triple-resonanc e NMR experiments combined with a semi-automatic assignment procedure yielded the sequential assignment of the H-1, C-13 and N-15 backbone r esonances. Based on the evaluation of conformationally sensitive param eters, the secondary structure of the IIBMan domain has been determine d as an alpha/beta twisted open-sheet structure consisting of a six-st randed parallel beta-sheet with the novel strand order 3-2-4-1-5-6, si x helices and a short two-stranded antiparallel beta-sheet. (C) 1997 F ederation of European Biochemical Societies.