This superfamily entry includes the ribosomal protein L30 found in the large (50S) subunit of the bacterial ribosome, as well as L7, the eukaryotic homologue found in the 60S subunit. The superfamily also contains archaeal L30 (the archaeal L30 contains an additional C-terminal subdomain), yeast mitochondrial L33, and Drosophila melanogaster, Dictyostelium discoideum (Slime mold), fungal and mammalian L7 ribosomal proteins. L30 from bacteria are small proteins of about 60 residues, those from archaea are proteins of about 150 residues, and eukaryotic L7 are proteins of about 250 to 270 residues. Despite not being a ribosomal protein, Rlp7, a nucleolar protein in Saccharomyces cerevisiae was found to have extensive similarity to L7, sharing the RNA-binding domain PMID:11087857.

Structurally, L30/L7 exhibits a ferredoxin-like fold, with a core structure consisting of core: beta-alpha-beta-alpha-beta. The protein contains a three-stranded antiparallel beta-sheet flanked by two alpha-helices on one side (referred to as the 'alpha-side' of the molecule) and exposed on the other (referred to as the 'beta-sheet side' of the molecule). The protein includes a split beta-alpha-beta motif with a role in the interaction with rRNA; the motif was found in other ribosomal proteins, such as S6, L1, L6, L9 and L22.

L30 is one of the smallest ribosomal proteins, with a molecular mass of about 7 kDa. L30 is not a core ribosomal protein. Its binding site on the ribosomal RNA is unknown, but cross-linking experiments indicate that elongation factor Tu can be cross-linked to an extended ribosome neighbourhood containing L30. The binding site is though to involve other ribosomal protein-protein interactions and/or rRNA interactions PMID:10531479.

PFAM:PF00327, INTERPRO:IPR036919,PMID:10531479