Crystal structure study of Opsanus tau parvalbumin by multiwavelength anomalous diffraction

Abstract

The crystal structure of a small calcium-binding protein, the parvalbumin I& from Opsanus tau in which Tb was substituted for Ca, has been analysed by multiwavelength anomalous diffraction. Data at a resolution of 2.3 A were collected at three wavelengths near the L, absorption edge of Tb (1.645-1.650 A), using the synchrotron radiation emitted by a storage ring and a multiwire proportional counter. The phases of the reflections were determined from this single derivative, without native data. Prior to any refinement, the resulting electron density map shows a good agreement with the model of the homologous carp parvalbumin in regions of identical amino-acid sequence.

A brief history of macromolecular crystallography, illustrated by a family tree and its Nobel fruits

“…The first successful application of the single-wavelength anomalous diffraction approach to proteins (based on the minute anomalous signal of sulfur) led him to the solution of the structure of crambin [64]. Two other groups of investigators, Roger Fourme (1942-2012) and colleagues [65], as well as Mitchell Guss and his collaborators [66], solved protein crystal structures using the multi-wavelength anomalous diffraction approach. This technique was further refined and popularized by Hendrickson and colleagues [67].…”

The prominent role of resonant elastic scattering for solving the X-ray structure of macromolecules

“…The development of MAD methods is indeed parallel to the progress of this instrumentation, in addition to progress in software. The first MAD phasing of a protein structure was achieved at the French synchrotron facility LURE at Orsay, and published in 1985 by R. Kahn et al [9].…”

“…Structure of the protein parvalbumin. Grey balls are Ca ions which were replaced by Tb ions for MAD phasing [9]. in the protein, and the structure of the complex was solved by MAD at the Se Kedge [12].…”

“…Compared to one selenium atom, and assuming that the diffraction data are collected at the respective absorption edge, a lanthanide atom will allow a protein that is nine times larger to be phased [13]. As mentioned, lanthanide ions were used in early MAD studies [9,11] as they can substitute for Ca 2+ . However, incorporation of lanthanides by using lanthanide salts often damages protein crystals, owing to the preferred nine-based coordination of lanthanide ions.…”

A MAD experiment performed at the white line of the iridiumLIIIabsorption edge in lysozyme

“…This method and a phasing approach analagous to MIR were used in the solution of Opsanus tau parvalbumin by MAD (Kahn et al, 1985). Two Ca atoms were substituted by Tb which has a large white line at its L III edge (f HH = 19.9 e).…”