Redox regulation of CrhR protein accumulation. Synechocystis cell-free extracts were obtained from cultures grown in the presence or absence of light and/or Glc or 3-OMG, as indicated. Total protein (15 μg) was separated on a 10% (w/v) SDS-PAGE gel, transferred to a nitrocellulose membrane, and immunostained with polyclonal antiserum generated against a CrhR His-tagged fusion protein. The 55-kD immunoreactive polypeptide corresponding to CrhR is shown. W, White light; D, darkness.