{HEAD ~ Box B} lies 21 amino acids C terminal to {TAIL ~ Box A} from amino acids 43 139 
{ HEAD ~ Box B } lies 21 amino acids C terminal to { TAIL ~ Box A } from amino acids 43 139
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH