X-ray absorption studies of halide binding to carbonic anhydrase.
X-ray absorption measurements of bovine carbonic anhydrase B have been made at the the Stanford Synchrotron Radiation Project with a spectrometer operating in the fluorescence mode. Differences in absorption at and beyond the zinc K-edge near 9664 ev have been observed upon the addition of bromide or iodide. The additional absorption in k space, out to k approximately 7 A-1, obtained upon the addition of iodide has been compared with the absorption in this region of a ZnI2 sample. The similarities between these absorptions lead to the conclusion that the zinc-iodide distance in the protein is 2.65 +/-0.06 A; it is known to be 2.62 A in ZnI2. This shows that the iodide binds directly to the zinc in the protein.
D000818:Animals; D001665:Binding Sites; D002256:Carbonic Anhydrases / Q000378:metabolism*; D002417:Cattle; D005583:Fourier Analysis; D007454:Iodides / Q000378:metabolism*; D008024:Ligands; D013053:Spectrophotometry; D014965:X-Rays; D015032:Zinc / Q000378:metabolism*
D007454:Iodides; D008024:Ligands; D002256:Carbonic Anhydrases; D015032:Zinc