Repression of RNA Polymerase II Transcription by a Drosophila Oligopeptide
Figure 1
The pgc locus encodes an alpha-helical monomeric and dimeric oligopeptide protein.
(A) pgc contains two open reading frames, encoding potential 71 and 75 residue oligopeptide proteins (Pgc ORF1 and ORF2, respectively). (B) The two candidate oligopeptides are predicted to contain alpha-helical secondary structure. (C) E. coli expressed and purified Pgc ORF1 is a soluble protein, in contrast to ORF2, which fails to refold in vitro. (D) Size-exclusion chromatography of PGC ORF1 reveals two chromatographic species, one migrating at 18 kDa, the other at 36 kDa, consistent with monomer and dimer fractions of (His)6-tagged Pgc ORF1. Absorbance signal at 280 nm (blue) and 260 nm (red). (E) Far-UV circular dichroism spectroscopy spectrum of purified, recombinant PGC ORF1 reveals that recombinant Pgc ORF1 protein contains intrinsic alpha-helical structure. Peak *1 (red), corresponding to the dimeric Pgc ORF1 complex, contains a higher alpha-helical content than monomeric Pgc1 (peak *2, blue).