InterPro domain: IPR036164

In Escherichia coli, L21 is known to bind to the 23S rRNA in the presence of L20. It belongs to a family of ribosomal proteins which, on the basis of sequence similarities, groups:

• Bacterial L21.
• Marchantia polymorpha chloroplast L21.
• Cyanelle L21.
• Plant chloroplast L21 (nuclear-encoded).

Bacterial L21 is a protein of about 100 amino-acid residues, the mature form of the spinach chloroplast L21 has 200 residues.

This superfamily includes large ribosomal subunit protein L21 and mitochondrial ribosomal subunit from yeast L49 (Mrpl49). In S. pombe, the putative mitochondrial ribosomal protein bL21 (Mrpl49) is fused to aconitase [ 1 ]. L21 has a small beta-barrel-like domain that is connected to an extended loop [ 2 ].

1. Essential function of Aco2, a fusion protein of aconitase and mitochondrial ribosomal protein bL21, in mitochondrial translation in fission yeast. FEBS Lett. 589, 822-8
2. High resolution structure of the large ribosomal subunit from a mesophilic eubacterium. Cell 107, 679-88