sentence: Furthermore , it is reasonable that the production of the G1A , R7A and W9A variants was not detected because the amino acid residues are proximal to the ring junction , and they might interact with the enzyme LarD in the maturation step of lariatin A.All lariatin variants were produced that contained substitutions of the residues in the β - turn motif ( Gly11 , His12 , Ser13 ) .