Figure 6.

RNA Binding Assay for Four Representative Arabidopsis PPR Proteins.

Two of these proteins (At1g79540 and At5g12100) are P subfamily members. At3g25970 is an E+ protein, and At5g13270 is a DYW protein.

(A) Radioactively labeled protein retained on Sepharose columns carrying various polyribonuculeotides, single-stranded DNA (ssDNA), or double-stranded DNA (dsDNA). The left lane was loaded with one-tenth of the protein loaded on the columns. The far right lane shows binding to a Sepharose column lacking added nucleotides. mRBP2b is a previously characterized RNA binding protein of the RNA recognition motif family, used here as a positive control. The bottom panel shows binding of β-glucuronidase (GUS) as a negative control.

(B) Competition assays for At5g12100. Labeled proteins were preincubated with competitor RNA or heparin before being loaded on a poly(G) Sepharose column and binding quantified by a phosphoimager, using binding in absence of competitor as 100%.