Essential protein with sulfite reductase activity required in assimilatory sulfate reduction pathway during both primary and secondary metabolism and thus involved in development and growth. DNA-binding protein that binds to both double-stranded and single-stranded DNA without significant sequence specificity to reversibly repress the transcriptional activity of chloroplast nucleoids by promoting DNA compaction and possibly regulate DNA replication. 3 H2O + hydrogen sulfide + 6 oxidized [2Fe-2S]-[ferredoxin] = 7 H(+) + 6 reduced [2Fe-2S]-[ferredoxin] + sulfite Binds 1 siroheme per subunit. Binds 1 [4Fe-4S] cluster per subunit. Exhibits a smaller absorbance peak at 587 nm. This absorption spectrum indicates the presence of a siroheme-containing prosthetic group. Monomer. Interacts with ferredoxin (By similarity). Phosphorylated; this phosphorylation reduces DNA-binding. Belongs to the nitrite and sulfite reductase 4Fe-4S domain family.