Var1 protein domain

VAR1
Identifiers
Symbol VAR1
Pfam PF05316
InterPro IPR007980

In molecular biology, VAR1 protein domain, otherwise known as variant protein 1, is a ribosomal protein that forms part of the small ribosomal subunit in yeast mitochondria. Mitochondria possess their own ribosomes responsible for the synthesis of a small number of proteins encoded by the mitochondrial genome. VAR1 is the only protein in the yeast mitochondrial ribosome to be encoded in the mitochondria - the remaining approximately 80 ribosomal proteins are encoded in the nucleus.[1] VAR1 along with 15S rRNA are necessary for the formation of mature 37S subunits.[2]

Function

It is thought that Var1 plays a role in the early steps of small subunit assembly and is required for the incorporation of at least one ribosomal protein. It is important for mitochondrial translational initiation, since it requires the interaction between the small ribosomal subunit and the message-specific translation factors.[1]

Ribosomal proteins in translation

Ribosomes are the organelles that catalyse mRNA-directed protein synthesis in all organisms. The codons of the mRNA are exposed on the ribosome to allow tRNA binding. This leads to the incorporation of amino acids into the growing polypeptide chain in accordance with the genetic information. Incoming amino acid monomers enter the ribosomal A site in the form of aminoacyl-tRNAs complexed with elongation factor Tu (EF-Tu) and GTP. The growing polypeptide chain, situated in the P site as peptidyl-tRNA, is then transferred to aminoacyl-tRNA and the new peptidyl-tRNA, extended by one residue, is translocated to the P site with the aid the elongation factor G (EF-G) and GTP as the deacylated tRNA is released from the ribosome through one or more exit sites.[3][4] Since Var1 helps form the small subunit of the ribosome, its significance become apparent in translation and cell survival.

References

  1. 1 2 Mason TL, Pan C, Sanchirico ME, Sirum-Connolly K (December 1996). "Molecular genetics of the peptidyl transferase center and the unusual Var1 protein in yeast mitochondrial ribosomes". Experientia. 52 (12): 1148–57. doi:10.1007/bf01952114. PMID 8988258.
  2. ↑ Davis SC, Ellis SR (May 1995). "Incorporation of the yeast mitochondrial ribosomal protein Mrp2 into ribosomal subunits requires the mitochondrially encoded Var1 protein". Mol. Gen. Genet. 247 (3): 379–86. doi:10.1007/bf00293206. PMID 7770043.
  3. ↑ Ramakrishnan V, Moore PB (April 2001). "Atomic structures at last: the ribosome in 2000". Curr. Opin. Struct. Biol. 11 (2): 144–54. doi:10.1016/s0959-440x(00)00184-6. PMID 11297922.
  4. ↑ Maguire BA, Zimmermann RA (March 2001). "The ribosome in focus". Cell. 104 (6): 813–6. doi:10.1016/s0092-8674(01)00278-1. PMID 11290319.

This article incorporates text from the public domain Pfam and InterPro IPR007980

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