Date of Graduation
Doctor of Philosophy in Chemistry (PhD)
Chemistry & Biochemistry
Second Committee Member
Third Committee Member
Fourth Committee Member
Fifth Committee Member
Targeting of proteins is a critical component of cellular function. A universally conserved targeting system of the cytosol utilizes a signal recognition particle (SRP) to target many proteins contranslationally to the endoplasmic reticulum in eukaryotes or the inner membrane in prokaryotes. A homologous SRP system exists in the chloroplast that delivers light harvesting chlorophyll binding proteins (LHCP) to they thylakoid membrane. The chloroplast SRP (cpSRP) is a heterodimer composed of a novel 43 kDa subunit and a 54 kDa subunit homologous to a component of the SRP system, SRP54. Many details regarding the interactions between the proteins of the cpSRP system have been determined. However, the three-dimensional arrangement of the cpSRP43 and cpSRP54 domains as well as their influence on one another has not been determined. The results of this study demonstrate both cpSRP43 and cpSRP54 are characterized by a significant amount of structural flexibility. Specifically, the domains of cpSRP43 and cpSRP54 are flexibly linked allowing for rapid conformational sampling of the domains. This flexibility allows cpSRP43 to sense the presence of cpSRP54 and subsequently alter its affinity for LHCP. Conversely, cpSRP54 domain flexibility allows it to scan cpSRP43 for the third transmembrane segment of LHCP in a manner surprisingly similar to SRP54 scanning for signal sequences at the ribosome. Together, the results of this structural investigation of the free and bound proteins has lead to the speculation of a cpSRP-LHCP transit complex structure capable of rationalizing the steps leading to the integration of LHCP.
Henderson, Rory, "Interactions in the cpSRP Dependent Targeting of Light Harvesting Chlorophyll Binding Protein to the Thylakoid Membrane" (2016). Theses and Dissertations. 2641.
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