Fluorescence studies on the interaction of adenine with ricin A-chain.
Ricin A-chain, an N-glycosidase that attacks 28S rRNA at a highly conserved adenine residue, has a unique tryptophan (Trp-211) in the putative active site cleft. Fluorescence spectroscopy revealed that specific binding of adenine to the A-chain caused a large enhancement of Trp-211 fluorescence (70%) and a concomitant red shift of the emission spectrum (8 nm). A Scatchard plot of the fluorescence enhancement data was not linear, indicating that the environment of Trp-211 was altered by heterogeneous binding of adenines. These results, taken together with the protective effect of adenine on the ribosome-inactivation by ricin A-chain, suggest that at least two adenines bind to the active site cleft.
Watanabe
K
K
Department of Applied Biological Sciences, Saga University, Japan.
Honjo
E
E
Tsukamoto
T
T
Funatsu
G
G
D000225:Adenine / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D037121:Plant Lectins; D010947:Plants, Toxic; D014176:Protein Biosynthesis / Q000187:drug effects; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism; D012276:Ricin / Q000378:metabolism*; D012278:Ricinus; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000378:metabolism
D037121:Plant Lectins; D014364:Tryptophan; D012276:Ricin; D000225:Adenine