Ribosome association of ProQ after mRNA disruption.
(A) Cell lysates were left untreated (solid line) or treated with limited MNase (dashed line) and ribosomal species separated on sucrose gradients. The positions of ProQ and ribosomal protein S2 in the resulting TCA-precipitated fractions is determined by western-blot analysis. (B) mRNA free 70S ribosomes were mixed with equimolar amounts of purified ProQ without (foreground) or with (background) the addition of equimolar P2 mRNA before application to sucrose gradients. The position of ProQ and ribosomal protein S2 in the resulting TCA-precipitated fraction is determined by western-blot analysis.