BIOORGANIC & MEDICINAL CHEMISTRY Pergamon Bioorganic & Medicinal Chemistry Letters 9 (1999) 2859-2862 LETrERS INTERACTION OF TYROSYL ARYL DIPEPTIDES WITH S. AUREUS TYROSYL tRNA SYNTHETASE: INHIBITION AND CRYSTAL STRUCTURE OF A COMPLEX Richard L. Jarvest, a* John M. Berge, a Catherine S.V. Houge-Frydrych, a Cheryl Janson, b Lucy M. Mensah, a Peter J. O'Hanlon, a Andrew Pope, a Adrian Saldanha, a and Xiayang Qiu b SmithKline Beecham Pharmaceuticals, a. New Frontiers Science Park, Third Avenue, Harlow, Essex, CMI9 5AW, UK b. King of Prussia, Pennsylvania 19406, USA Received 1 June 1999; accepted 1 September 1999 Abstract: Tyrosyl aryl dipeptide inhibitors ofS. aureus tyrosyl tRNA synthetase have been identified with IC50 values down to 0.5 laM. A crystal structure of the enzyme complexed to one of the inhibitors shows occupancy of the tyrosyl binding pocket coupled with inhibitor interactions to key catalytic residues. © 1999 ElsevierScience Ltd. All rights reserved. Aminoacyl tRNA synthetases catalyse the attachment of a proteinergic amino acid to its cognate tRNA, an essential step in protein biosynthesis. Tyrsoyl tRNA synthetase, like other members of the family, carries out the reaction in a two stage process via formation of an aminoacyl adenylate intermediate (Tyr-AMP; 1). The aminoacyl tRNA synthetases are divided into two classes determined by different signature motifs and three dimensional structures. 1 Tyrosyl tRNA synthetase is a member of the Class I tRNA synthetases which are characterised by catalytically important HIGH and KMSKS sequence motifs. tRNA Tyr + ATP + E ..... E.Tyr-AMP .... AMP + Tyr-tRNA + E -k PPi Although aminoacyl tRNA synthetases perform an essential role in the cellular biochemistry of all organisms there are significant structural differences between bacterial and mammalian enyzmes, so that selective inhibition oftRNA synthetases offers potential for a new antibacterial therapy. Staphylococcus aureus is a key Gram positive bacterial pathogen and we selected the design of novel inhibitors of the S. aureus tyrosyl tRNA synthetase as a possible therapeutic approach. Stabilised mimics of the intermediate adenylate such as tyrosinyl adenylate are potent inhibitors of tyrosyl tRNA synthetase2-4 but their polarity prevents their transport across the bacterial cell wall. Some tyrosyl dipeptides have been reported to inhibit E. coli tyrosyl tRNA synthetase with Ki values ranging from 4 - 100 :M. 3 Here we report novel sub-micromolar dipeptide inhibitors of S. aureus tyrosyl tRNA synthetase and the mode of inhibition as characterised by an X-ray crystal structure of an enzyme-inhibitor complex. HO,~ NH2 H{~ OH e-mail:Richard L Jarvest~bphrd.com Fax +44 1279 627628. 0960-894X/9915 - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0960-894X(99)00488-6