Ribonucleoprotein

Ribonucleoprotein (RNP) is a nucleoprotein that contains RNA, i.e. it is an association that combines a ribonucleic acid and an RNA-binding protein together. Such a combination can also be referred to as a protein-RNA complex. These complexes play an integral part in a number of important biological functions that include DNA replication, regulating gene expression and regulating the metabolism of RNA. A few examples of RNPs include the ribosome, the enzyme telomerase, vault ribonucleoproteins, RNase P, hnRNP and small nuclear RNPs (snRNPs), which have been implicated in pre-mRNA splicing (spliceosome) and are among the main components of the nucleolus.

Currently, over 2000 RNPs can be found in the RCSB Protein Data Bank (PDB). Furthermore, the Protein-RNA Interface Data Base (PRIDB) possesses a collection of information on RNA-protein interfaces based on data drawn from the PDB. Some common features of protein-RNA interfaces were deduced based on known structures. For example, RNP in snRNPs have an RNA-binding motif in its RNA-binding protein. Aromatic amino acid residues in this motif result in stacking interactions with RNA. Lysine residues in the helical portion of RNA-binding proteins help to stabilize interactions with nucleic acids. This nucleic acid binding is strengthened by electrostatic attraction between the positive lysine side chains and the negative nucleic acid phosphate backbones. Additionally, it is possible to model RNPs computationally. Although computational methods of deducing RNP structures are less accurate than experimental methods, they provide a rough model of the structure which allows for predictions of the identity of significant amino acids and nucleotide residues. Such information helps in understanding the overall function the RNP.

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