The name of this superfamily has been modified since the most recent official CATH+ release (v4_3_0). At the point of the last release, this superfamily was: waiting to be named.
L1 is the largest protein from the large ribosomal subunit and structurally, it consists of one alpha/beta subdomain interrupted by another alpha/beta subdomain. In the structure of the protein, two domains are connected by a hinge region that consists of two oppositely directed polypeptide chains. L1 is a two-domain protein with N- and C-termini located in domain I. L1 has a dual function as a ribosomal protein binding 23S rRNA and as a translational repressor binding its mRNA. L1 from Escherichia coli (EcoL1) mediates autogenous regulation of translation by binding to a region within the leader sequence, close to the Shine-Dalgarno sequence, of the mRNA of the L11 operon coding for ribosomal proteins L1 and L11 PMID:15659579.
This superfamily entry represents the rRNA-binding domain, also called domain I. The isolated domain I has a two-layer structure. One of the layers is formed by a four-stranded anti-parallel beta-sheet, the other contains two alpha-helices. The N-terminal alpha-helix shields the interlayer region from one side, whereas two anti-parallel beta-strands cover it from the other side. It has been shown that domain I is necessary and sufficient for specific RNA-binding by L1, due to the formation of stable complexes with the isolated domain I forms stable complexes and specific fragments of both rRNA and mRNA. Experimental evidence suggests that in protein L1 its domain I alone is sufficient for specific RNA binding, whereas domain II stabilises the L1-rRNA complex. Other studies suggest that L1 interacts with the 23S rRNA through both of its domains PMID:12514741.
|Domain clusters (>95% seq id):||12|
|Domain clusters (>35% seq id):||5|
|Structural Clusters (5A):||2|
|Structural Clusters (9A):||1|