The secondary structure of the colicin E3 immunity protein as studied by 1H-1H and 1H-15N two-dimensional NMR spectroscopy.
By performing 1H-1H and 1H-15N two-dimensional (2D) nuclear magnetic resonance (NMR) experiments, the complete sequence-specific resonance assignment was determined for the colicin E3 immunity protein (84 residues; ImmE3), which binds to colicin E3 and inhibits its RNase activity. First, the fingerprint region of the spectrum was analyzed by homonuclear 1H-1H HOHAHA and NOESY methods. For the identification of overlapping resonances, heteronuclear 1H-15N (HMQC-HOHAHA, HMQC-NOESY) experiments were performed, so that the complete 1H and 15N resonance assignments were provided. Then the secondary structure of ImmE3 was determined by examination of characteristic patterns of sequential backbone proton NOEs in combination with measurement of exchange rates of amide protons and 3JHN alpha coupling constants. From these results, it was concluded that ImmE3 contains a four-stranded antiparallel beta-sheet (residues 2-10, 19-22, 47-49, and 71-79) and a short alpha-helix (residues 31-36).
Yajima
S
S
Department of Biotechnology, Faculty of Agriculture, University of Tokyo, Japan.
Muto
Y
Y
Yokoyama
S
S
Masaki
H
H
Uozumi
T
T
D000595:Amino Acid Sequence; D003087:Colicins / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012260:Ribonucleases / Q000737:chemistry / Q000648:ultrastructure
D003087:Colicins; D012260:Ribonucleases