Substrate specificity of the amino acyl adenylate activation sites of gramicidin S-synthetase (GSS).

An investigation was made of the intermolecular forces which determine substrate recognition and binding as well as of the topography and localized environment of the different binding sites of the substrate amino acids of gramicidin S-synthetase (GSS) using substrate derivatives as molecular probes. It is demonstrated that among the aminoacyl adenylate binding sites of the heavy component of GSS the activation site of L-ornithine is distinguished by a relatively high substrate variability. The active centres of GSS are less restrictive for the activation of substrate analogues modified at the carboxyl group than for derivatives substituted at the alpha-amino group.