Has a central role in coupling the hydrolysis of ATP to the transfer of proteins across the thylakoid membrane (PubMed:7758587, PubMed:7989297, PubMed:9342223). Facilitates the transport of precursor proteins from the chloroplast stroma to thylakoid lumen (PubMed:7758587, PubMed:7989297, PubMed:9342223). ATP + H2O + chloroplast-proteinSide 1 = ADP + phosphate + chloroplast-proteinSide 2. A minor fraction is associated with the chloroplast thylakoid membrane. Belongs to the SecA family.