Fig. 6. SmB-binding domain in Csul. (Upper panel) Full-length GST-Csul or derivatives were purified from bacteria and incubated with [³⁵S]S^*Tag-SmB. Bound [³⁵S]S^*Tag-SmB proteins were separated by SDS-PAGE and detected by fluorography. Amino acid numbers are given across the top. `Input' was one tenth of the synthesized [³⁵S]S^*Tag-SmB proteins. The smallest fragment of Csul showing binding to SmB encompasses amino acids 1-200. (Lower panel) The amount of GST-Csul polypeptides was visualized by Coomassie Blue staining. (Right) Representation of the GST-Csul fragments used for the mapping and the summary of the results, with the identified domain required for SmB-binding in Csul shown in blue.