Stereo view of the local environment around Cys-421. The structure of S-EIIB is superposed onto that of EIIB in the complex structure for this figure. Mlc is represented by a ribbon drawing, but, for clarity, only Cα tracing of the sheet of EIIB implicated in complex formation is shown. EIIB in the complex structure and S-EIIB are colored in violet and green, respectively. In EIIB bound to Mlc, only Arg-424 is shown for clarity. Dotted lines represent polar interactions between the bound sulfate ion and EIIB.