Binds the 23S rRNA. While neither of the L31 paralogs is essential, this protein seems to function as the main L31 protein. Has a lower affinity for 70S ribosomes than the non-zinc-containing paralog L31B (ytiA); is displaced by it to varying extents, even under zinc-replete conditions. Binds 1 zinc ion per subunit. This zinc stabilizes the protein. Part of the 50S ribosomal subunit during exponential growth. Only accumulates during exponential growth. Belongs to the bacterial ribosomal protein bL31 family. Type A subfamily.