bonding. This could have advantages for the expression of some proteins
and enrich the potential of the algal chloroplast as a production
platform. In chloroplasts, proteins are naturally targeted across the thylakoidmembrane
by the Sec or Tat pathways, and attachment of a Sec or
Tat signal peptide to a heterologous protein often results in correct
targeting and maturation (reviewed in [8]). Here, we used the TorA
Tat signal peptide from Escherichia coli, which has been used to direct
the export of biotechnologically relevant proteins to the periplasm in
E. coli (reviewed in [9]), as a targeting peptide to translocate recombinant
proteins into the thylakoid lumen of the C. reinhardtii chloroplast.
We show that the Tat signal peptide can target and translocate both a
fluorescent reporter protein, pHRed, and a biopharmaceutical (scFv antibody
fragment) into the thylakoid lumen of C. reinhardtii.