Fig. 6: Mimic-phosphorylation of H-loop inhibits NBCe1-A by interaction with IL3.

a Diagram showing the arrangement of TMs in NBCe1 TMD (bottom view). Yellow: TMs in the carrier domain. Green: TMs in the scaffold domain. H-loop is shown in red. IL3 is shown in blue. b Side view of NBCe1 TMD (partial). Note that H-loop is spatially close to TM6-IL3. Mutations to H-loop have no significant effect on the relative expression levels of total (c) and surface (d) NBCe1-A in oocytes. H-loop^3A: T⁸⁵⁹/T⁸⁶¹/S⁸⁶² substituted with Ala. H-loop^3D: T⁸⁵⁹/T⁸⁶¹/S⁸⁶² substituted with Asp. See Fig. S4c for full blots. e Mimic-phosphorylation of H-loop inhibits NBCe1-A activity. f, g Effect of mutations to IL3 on the activity of NBCe1-A with either H-loop^WT or H-loop^3D. h Summary of percentile inhibition of NBCe1-A by H-loop. The figure was created based on the data contributed to f and g. i Proposed model for the mechanism of NBCe1-A inhibition by phosphorylation of H-loop. Data are presented as mean ± SD. The numerals in the parentheses on the bars indicate the number of individual oocytes for activity data or the number of western blottings with independent pools of oocytes for expression data. ns, not significant by two-tailed student’s t-test in f and g. One-way ANOVA followed by post hoc Dunnett’s multiple comparisons was used for statistical analyses in h. **p < 0.01; ****p < 0.0001.