Abstract
X-ray intensity data from the native orthorhombic crystals of peanut lectin have been collected using oscillation photography. Rotation function studies using data up to a resolution of 4.5 A indicate that the four subunits in the molecule, which constitute the asymmetric unit in the crystals, are related to one another by three mutually perpendicular noncrystallographic 2-fold axes. Chemical cross-linking experiments in solution followed by sodium dodecyl sulfate gel electrophoresis, carried out in parallel, suggest that there is more than one type of intersubunit approach in the molecule. Rotation function and cross-linking studies thus show that the tetrameric molecule of peanut lectin is a dimer of a dimer. The two monomers in a dimer are related by a 2-fold axis. The two dimers are in turn related by another 2-fold axis perpendicular to the one that relates the two monomers in the dimer, endowing the molecule with 222 (D2) symmetry.
Highlights
EXPERIMENTALPROCEDURES crystals of peanut lectin have been collectedusing oscillation photography
Rotation function and cross-linking studies bic crystals were collected by oscillation photography using CuK, show that the tetrameric molecule of pleactniunt radiation from a Marconi Avionics rotating anode x-ray generator is a dimer of a dimer
The two dimers are related by another 2-fold axis perpendicular to in the tounrnercaenrsygosllteuaotlisfown9e0or”ef.,m2T.oh4ueAnotsewcdiiltlahabtioaountcratyhnsegtaleal-*vtoaa-xrfiiiesldmabndedtiwsrotaetneancteed2“otfharn7od5ug1mh.5ma”.,twToithtahel that relates the two monomers in the dimer, endowing 20%overlap between films. 28 crystals were used for data collection the inoleculewith 222 (Dz)symmetry
Summary
Rotation function and cross-linking studies bic crystals were collected by oscillation photography using CuK, show that the tetrameric molecule of pleactniunt radiation from a Marconi Avionics rotating anode x-ray generator is a dimer of a dimer. We crystallized two monoclinic forms and a triclinic form of the lectin at pH 4.6 (8).These forms contain a (longitude) define the direction, a rotation about which relates the two subunits. Self-rotation functions, using origin removed Patterson functions, were calculated employingthe Rossmann program for different values tetrameric molecule in the asymmetric unit, the of K, but only those with K = 180” contained interpretable peaks. Resolution limits and theradius of integration were varied, but the best results were obtained when data in the 10-4.5 A range were used with a radius of integration of 35 A This function, shown, is considered in the following discussion.
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