Figure 2
From: Monatomic ions influence substrate permeation across bacterial microcompartment shells
Salt influences the permeation of substrate across the Pdu BMC shell. (A) The apparent formation rate of propanal is dependent on the rate of permeation (kpermeation) of 1,2-propanediol across the shell and the rate of catalysis (kturnover) by the signature complex PduCDE. Propanal formation is monitored at 280 nm. (B) Electron micrographs of purified, intact Pdu BMCs and (C) BMCs broken by sonication. Activities in intact BMCs are affected by both kpermeation and kturnover while broken BMCs have kpermeation minimized leaving kturnover as the main consideration. (D) The initial velocity (V0) of propanal formation was monitored as a function of [NaCl]. A linear regression was performed on points between 100–500 mM NaCl, leading to significantly different slopes (P < 0.0001). Assays were performed in quadruplicate. (E) The ratio of V0’s between broken and native samples are not constant as a function of [NaCl], indicating both that broken samples are faster and that kpermeation is negatively affected by increasing NaCl. Error in (E) was compounded from (D). Panels (D) and (E) were generated in GraphPad Prism 9.
