ENZYME-IIB(CELLOBIOSE) OF THE PHOSPHOENOL-PYRUVATE-DEPENDENT PHOSPHOTRANSFERASE SYSTEM OF ESCHERICHIA-COLI - BACKBONE ASSIGNMENT AND SECONDARY STRUCTURE DETERMINED BY 3-DIMENSIONAL NMR-SPECTROSCOPY
E. Ab et al., ENZYME-IIB(CELLOBIOSE) OF THE PHOSPHOENOL-PYRUVATE-DEPENDENT PHOSPHOTRANSFERASE SYSTEM OF ESCHERICHIA-COLI - BACKBONE ASSIGNMENT AND SECONDARY STRUCTURE DETERMINED BY 3-DIMENSIONAL NMR-SPECTROSCOPY, Protein science, 3(2), 1994, pp. 282-290
The assignment of backbone resonances and the secondary structure dete
rmination of the Cys 10 Ser mutant of enzyme IIBCellobiose of the Esch
erichia coli cellobiose-specific phosphoenol-pyruvate-dependent phosph
otransferase system are presented. The backbone resonances were assign
ed using 4 triple resonance experiments, the HNCA and HN(CO)CA experim
ents, correlating backbone H-1, (SN)-S-15, and C-13(alpha) resonances,
and the HN(CA)CO and HNCO experiments, correlating backbone H-1, N-15
and (CO)-C-13 resonances. Heteronuclear H-1-NOE H-1-N-15 single quant
um coherence (N-15-NOESY-HSQC) spectroscopy and heteronuclear H-1 tota
l correlation H-1-N-15 single quantum coherence (N-15-TOCSY-HSQC) spec
troscopy were used to resolve ambiguities arising from overlapping C-1
3(alpha) and (CO)-C-13 frequencies and to check the assignments from t
he triple resonance experiments. This procedure, together with a 3-dim
ensional H-1 alpha-C-13 alpha-(CO)-C-13 experiment (COCAH), yielded th
e assignment for all observed backbone resonances. The secondary struc
ture was determined using information both from the deviation of obser
ved 1H alpha and C-13 alpha chemical shifts from their random coil val
ues and H-1-NOE information from the N-15-NOESY-HSQC. These data show
that enzyme IIBcellobiose consists of a 4-stranded parallel beta-sheet
and 5 alpha-helices. In the wild-type enzyme IIBcellobiose, the catal
ytic residue appears to be located at the end of a beta-strand.