Intrinsic fluorescence as a potential rapid scoring tool for protein crystals

Genomics is on the verge of creating a large number of proteins for structu re determination. Since X-ray crystallography is the main tool for determin ing protein structure, a corresponding large number of X-ray diffraction ex periments will have to be performed. However, X-ray analysis is labor inten sive so that the question of which protein crystal to choose for X-ray anal ysis from the vast pool of candidates becomes important from an economics s tandpoint. It is desirable to have a rapid and efficient method to score pr otein crystals regarding their likelihood for being of diffraction quality. We propose intrinsic protein fluorescence as a scoring tool and report pre liminary data that demonstrate correlation between fluorescence spectra of single crystals and their internal order as determined by X-ray crystallogr aphy. Specifically, fine structure and maxima of fluorescence emission spec tra of lysozyme, hyaluronate lyase, and germination protease crystals were found to correlate with resolution and mosaicity determined by X-ray analys is. If the correlation exhibited by these three proteins reflects a general relationship for the majority of protein crystals, a rapid fluorescence as say for scoring crystals can be developed and adapted for a variety of conf igurations of high throughput crystal growth apparatus. (C) 2001 Elsevier S cience B.V. All rights reserved.