Fig. 7. Cells from shi^ts animals arrest mBSA at the plasma membrane in cell-surface-accessible structures. (A) Cartoon depicting the scheme adopted for detecting surface accessibility of mBSA bound to ALBR using Cy5-SA and B-Cy3mBSA. (B) Histogram shows the ratio of Cy5 to Cy3 fluorescence obtained for shi^ts1 cells at the temperatures and conditions indicated. The cartoons indicate the expected surface-accessible or -inaccessible status of ALBR ligand (B-Cy3mBSA) as probed using Cy5-SA. (C) Histogram shows the average extent of B-Cy3mBSA bound to the cells that remains accessible to Cy5-SA (Cy5/Cy3 ratio) after a pulse for 5 minutes at 21°C and 31°C in the indicated alleles, relative to the total accessible pool of receptors (Cy5/Cy3 ratio determined for Ice condition; arrow). Bars represent mean±s.e. obtained from three experiments, each with at least 75 cells from two dishes in each condition Note that both shi^ts alleles quantitatively arrest Cy3mBSA internalization at this temperature.