Role of Competitive Interactions in Growth Rate Trends of Subtilsin s88 Crystals

Published

May 1, 2000

Author(s)

D Asthagirl, A Lenhoff, David Travis Gallagher

Abstract

An orthorhombic crystal form of subtilisin BPN' variant s88 exhibits a systematic variation in growth rates of its three unique faces, resulting in pronounced variations in crystal morphology as a function of the ionic strength. We have sought to explain these observations by performing energetics calculations using the full structural details of the protein. The approach of correlating growth rates with the strength of interactions of molecular pairs in the crystal proves unsatisfactory. The attachment of protein molecules to growing crystal faces is a stochastic process: a protein molecule samples numerous configurational (orientational and translational) states before attaching to the crystal in a configuration consistent with the crystal symmetry. This search-and-bind process determines the rate of crystal growth. We present a simplified approach that mimics this dynamical process: we perform docking of a protein molecule with another protein molecule or a cluster of molecules. An analysis of the bound configurations reveals the presence of orientations that are incommensurate with the crystal symmetry but in which a protein molecule can also bind strongly to the crystal face. Such improperly oriented molecules can be thought of as competitive inhibitors, and their presence is shown to affect the growth rate. Thus procedures aimed at decreasing the effect of such competitive inhibition, or conversely increasing the specificity of protein-protein interactions forming the crystal, are expected to offer better control of crystal growth rates.

Citation

Journal of Crystal Growth

Volume

212

Issue

3-4

Pub Type

Journals

Keywords

crystal contacts, crystal growth models, interaction energy, self-poisoning

Citation

Asthagirl, D. , Lenhoff, A. and Gallagher, D. (2000), Role of Competitive Interactions in Growth Rate Trends of Subtilsin s88 Crystals, Journal of Crystal Growth (Accessed December 14, 2024)