title: Long-range magnetization transfer between uncoupled nuclei by dipole-dipole cross-correlated relaxation: a precise probe of beta-sheet geometry in proteins.
abstract: Interference between dipolar interactions in covalently linked (13)C-(1)H and nonlinked (1)H-(1)H pairs can be used to generate antiphase magnetization between noncoupled spins. The buildup rate of such antiphase terms is highly sensitive to local geometry, in particular the interproton distance and the (13)C-(1)H-(1)H internuclear angle. These rates have been measured for opposing C(alpha)H(alpha) pairs in antiparallel beta-sheets in the third Igg-binding domain of protein G (GB3) and in HIV protease, complexed with the inhibitor DMP323. For GB3, good agreement with the 1.1-A crystal structure is found. However, this agreement rapidly deteriorates with decreasing resolution of the corresponding X-ray structure. For HIV protease, two separate crystal structures that differ by less than 0.2 A from one another exhibit lower agreement in their predicted cross-correlated relaxation rates relative to one another than is found between experimental rates and the average of the rates predicted for the two structures. These data indicate that quantitative measurement of these cross-correlated relaxation rates can provide highly accurate structural information in macromolecules.
authors.affiliation: Contribution from the Laboratory of Chemical Physics, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, USA.
authors.forename: Jerome
authors.initials: J
authors.lastname: Boisbouvier
authors.forename: Ad
authors.initials: A
authors.lastname: Bax
mesh_terms: D002247:Carbon Isotopes; D016333:HIV Protease / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D017433:Protein Structure, Secondary; D011522:Protons
chemical_list: D002247:Carbon Isotopes; C029152:G-substrate; D009419:Nerve Tissue Proteins; D011522:Protons; D016333:HIV Protease