Figure 4.

RNA-binding characteristics of the CS1 protein. RNA binding was analyzed using the UV-crosslinking competition assay. The 30S fraction (CS1) or the recombinant CS1 protein (recCS1) were mixed with synthetic [³²P]RNA representing the psbA 5′-UTR in the presence of non-radioactive competitor RNA, as indicated in the figure. No competitor was added in the lane marked –. Following incubation, the reaction mixture was UV-crosslinked, digested with RNase and analyzed by SDS–PAGE and autoradiography. KS-T3 indicates RNA containing 14 uridines that was transcribed using T3 RNA polymerase from plasmid Bluescript linearized with BamHI. KS-T7 represents RNA containing eight uridines that was transcribed from the same plasmid using T7 RNA polymerase.