The Light Harvesting Chlorophyll a/b-binding Proteins (LHCPs) are the most abundant membrane proteins on earth and are highly prone to aggregation in aqueous solution due to their hydrophobic nature. Biogenesis of membrane proteins poses a special challenge to protein homeostasis. Before arrival at their target membrane, membrane proteins must travel through one or more aqueous cellular environments where they are highly prone to aggregation and misfolding, necessitating the actions of highly effective molecular chaperones to keep them soluble and translocation competent. A hypothesis has been proposed that the LHCP Translocation Defect (LTD) protein is a membrane protein chaperone that captures LHCP upon entry into the stroma and delivers LHCP to the chloroplast signal recognition particle (cpSRP) complex. However, this hypothesis cannot be supported by our pull-down, light scattering, fluorescence anisotropy, and Fluorescence Resonance Energy Transfer (FRET) assays. Instead, we present evidence that LTD is not performing chaperone activity. We suspect that LTD is itself a highly aggregation prone protein and suggest that this is the reason for its observed association with the cpSRP complex. We further surmise that a chaperone from the Heat Shock Protein (HSP) family may be present to facilitate LHCP translocation and handover the substrate to cpSRP during protein targeting pathway.

LTD does not function as a membrane protein chaperone during protein targeting in the chloroplast

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.