Fig. 1.

(A) Structures of streptolydigin (compound 1) and novel derivative streptolydigin B (compound 2). (B) Schematic representation of SlgZ (S. lydicus), AsnRS2, and AsnRS (P. abyssi). A sequence comparison of three characteristic motifs present in the catalytic core is shown. The invariant residues from each motif are indicated by black circles. (C) Supply of amino acid precursor for the biosynthesis of streptolydigin. A′, SlgN1 adenylation domain; A, SlgN2 adenylation domain; C, condensation domain; PCP, peptidyl carrier protein.