Fig. 5.

Identification of the autoinhibitory peptide XIP. (A) Time course of the Ca²⁺ transport assay of YfkE^WT measured using ISO vesicles pretreated with 1 mM EGTA in the presence of 5 μM synthetic peptide of the XIP or its acidic motif. (B) YfkE activity as a function of [XIP] using vesicles treated with 1 mM EGTA. Data fitting into single exponential decay using the software Graphpad Prism 7. (C) Theme of the XIP modification by phenylglyoxal. (D) Ca²⁺ transport activity of YfkE^WT measured with vesicles (20 min) treated with (+) or without (−) EGTA in the presence of 5 μM XIP or modified peptide XIP-dicarbonyl phenylgyoxal (PGO). (E) Fluorescence (λ_ex/λ_em: 555/677 nm) changes (%) of labeled YfkE^A190C protein as a function of [XIP]. The XIP peptide was added before (circles) or after adding 100 μM Ca²⁺ (squares). Error bars represent SDs from three independent experiments.