A Dynamic cpSRP43-Albino3 Interaction Mediates Translocase Regulation of Chloroplast Signal Recognition Particle (cpSRP)-targeting Components
by Lewis, Nathaniel E.; Marty, Naomi J.; Kathir, Karuppanan Muthusamy; Dakshinamurthy, Rajalingam; Kight, Alicia D.; Daily, Anna E.; Kumar, Thallapuranam Krishnaswamy Suresh; Henry, Ralph L.; Goforth, Robyn L.
The chloroplast signal recognition particle (cpSRP) and its receptor, chloroplast FtsY (cpFtsY), form an essential complex with the translocase Albino3 (Alb3) during post-translational targeting of light-harvesting chlorophyll-binding proteins (LHCPs). Here, we describe a combination of studies that explore the binding interface and functional role of a previously identified cpSRP43-Alb3 interaction. Using recombinant proteins corresponding to the C terminus of Alb3 (Alb3-Cterm) and various domains of cpSRP43, we identify the ankyrin repeat region of cpSRP43 as the domain primarily responsible for the interaction with Alb3-Cterm. Furthermore, we show Alb3-Cterm dissociates a cpSRP.LHCP targeting complex in vitro and stimulates GTP hydrolysis by cpSRP54 and cpFtsY in a strictly cpSRP43-dependent manner. These results support a model in which interactions between the ankyrin region of cpSRP43 and the C terminus of Alb3 promote distinct membrane-localized events, including LHCP release from cpSRP and release of targeting components from Alb3.
- Journal of Biological Chemistry
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- 1083-351X; 0021-9258