Nuclear genome-encoded factor required for normal assembly of chloroplast polysomes. ATP + L-cysteine + tRNA(Cys) = AMP + diphosphate + L-cysteinyl-tRNA(Cys) Binds 1 zinc ion per subunit. The cps1 mutant phenotype resembling other non-photosynthetic mutants, CPS1 may function solely in chloroplasts. Pale green leaf phenotype. Global defects in chloroplast translation. Belongs to the class-I aminoacyl-tRNA synthetase family.