Cytosolic chaperones interact with newly synthesized β-barrel proteins. (A and B) In vitro translation reactions using yeast extracts without mRNA (Ø) or programmed with mRNA encoding DHFR-HA (D), Porin-HA (P), Tom40-HA (40), Tob55Δ120-HA (55), Om14-HA (O), Cyc3-HA (C), Tim23-HA (T), or Yah1-HA (Y) were subjected to a pull-down with anti-HA beads. Samples from the input and the eluates were analyzed by SDS-PAGE and immunodecoration with the indicated antibodies. (C) Yeast extracts programmed with mRNA encoding for Porin-HA were incubated for the indicated times. Afterward, the reactions were subjected to an anti-HA pull-down and analyzed as in A. (D) Yeast extracts were incubated with the indicated Bpa-containing peptide at the specified concentrations. Some samples were either illuminated with UV light (+UV) to induce cross-linking or were left in darkness (−UV). Then, the samples were analyzed by SDS-PAGE and immunodecoration with the indicated antibodies. PA, specific photoadducts.