Although a 26-bp near-perfect palindromic region from 102 to 77 exists upstream of argO ( see Fig. 1A ) , neither its deletion  nor that of an overlapping 1260 GENES & DEVELOPMENT upstream region from 115 to 90  led to any significant loss of either ArgP binding to argO in-vitro ( Fig. 2B ) or to Arg-and Lys-modulated transcriptional regulation in-vivo ( Fig. 1B , top panel ) .