S4 protein domain explained

Symbol:	S4
S4
Width:	350 px
Pfam:	PF01479
Pfam Clan:	CL0492
Interpro:	IPR002942
Prosite:	PDOC00549
Scop:	1c06
Cdd:	cd00165

In molecular biology, S4 domain refers to a small RNA-binding protein domain found in a ribosomal protein named uS4 (called S9 in eukaryotes). The S4 domain is approximately 60-65 amino acid residues long, occurs in a single copy at various positions in different proteins and was originally found in pseudouridine syntheses, a bacterial ribosome-associated protein.^[1]

The S4 protein helps to initiate assembly of the 16S rRNA. In this way proteins serve to organise and stabilise the rRNA tertiary structure.^{[2] [3]}

Function

The function of the S4 domain is to be an RNA-binding protein. S4 is a multifunctional protein, and it must bind to the 16S ribosomal RNA. In addition, the S4 domain binds a complex pseudoknot and represses translation. More specifically, this protein domain delivers nucleotide-modifying enzymes to RNA and to regulates translation through structure specific RNA binding.^[1]

Structure

The S4 protein domain is composed of three alpha helices and five beta strands. It is organized as an antiparallel sheet in a Greek key motif.^[4]

Notes and References

1. Aravind L, Koonin EV . Novel predicted RNA-binding domains associated with the translation machinery . J. Mol. Evol. . 48 . 3 . 291–302 . March 1999 . 10093218 . 10.1007/pl00006472. 8083860 .
2. Maguire BA, Zimmermann RA . The ribosome in focus . Cell . 104 . 6 . 813–6 . March 2001 . 11290319 . 10.1016/s0092-8674(01)00278-1. 8174178 . free .
3. Chandra Sanyal S, Liljas A . The end of the beginning: structural studies of ribosomal proteins . Curr. Opin. Struct. Biol. . 10 . 6 . 633–6 . December 2000 . 11114498 . 10.1016/S0959-440X(00)00143-3.
4. Davies C, Gerstner RB, Draper DE, Ramakrishnan V, White SW . The crystal structure of ribosomal protein S4 reveals a two-domain molecule with an extensive RNA-binding surface: one domain shows structural homology to the ETS DNA-binding motif. . EMBO J . 1998 . 17 . 16 . 4545–58 . 9707415 . 10.1093/emboj/17.16.4545 . 1170785 .