Banci L

Bertini I

Ciofi-Baffoni S

Kandias NG

Robinson NJ

Spyroulias GA

Su X-C

Tottey S

Vanarotti M

The thylakoid compartments of plant chloroplasts are a vital destination for copper. Copper is needed to form holo-plastocyanin, which must shuttle electrons between photosystems to convert light into biologically useful chemical energy. Copper can bind tightly to proteins, so it has been hypothesized that copper partitions onto ligand-exchange pathways to reach intracellular locations without inflicting damage en route. The copper metallochaperone Atx1 of chloroplast-related cyanobacteria (ScAtx1) engages in bacterial two-hybrid interactions with N-terminal domains of copper-transporting ATPases CtaA (cell import) and PacS (thylakoid import). Here we visualize copper delivery. The N-terminal domain PacSN has a ferredoxin-like fold that forms copper-dependent heterodimers with ScAtx1. Removal of copper, by the addition of the cuprous-ion chelator bathocuproine disulfonate, disrupts this heterodimer, as shown from a reduction of the overall tumbling rate of the protein mixture. The NMR spectral changes of the heterodimer versus the separate proteins reveal that loops 1, 3, and 5 (the carboxyl tail) of the ScAtx1 Cu(I) site switch to an apo-like configuration in the heterodimer. NMR data ( 2JNH couplings in the imidazole ring of 15N ScAtx1 His-61) also show that His-61, bound to copper(I) in [Cu(I)ScAtX1] 2, is not coordinated to copper in the heterodimer. A model for the PacSN/Cu(I)/ScAtx1 complex is presented. Contact with PacS N induces change to the ScAtx1 copper-coordination sphere that drives copper release for thylakoid import. These data also elaborate on the mechanism to keep copper(I) out of the ZiaAN ATPase zinc sites. \ua9 2006 by The National Academy of Sciences of the USA

Newcastle University E-Prints

The delivery of copper for thylakoid import observed by NMR

The delivery of copper for thylakoid import observed by NMR

Abstract

Similar works

Full text

Available Versions

Newcastle University E-Prints