Ltn1p

E3 ubiquitin protein ligase listerin
other names	RING domain mutant killed by rtf1 deletion protein 1
	Existing structural data : PDB 5FG0 , PDB 5FG1
Mass / length primary structure	1,562 amino acids , 180,186 Da
Identifier
External IDs	UniProt : Q04781 ;
Enzyme classification
EC, category	2.3.2.27

Ltn1p is a protein in yeast that is involved in quality control of newly formed proteins during and after protein biosynthesis on ribosomes .

properties

The translation from mRNA to protein takes place on ribosomes. It comes to a standstill due to mRNA without a stop codon , the entire protein synthesis stops and only a few lysines are added to the faulty protein that is formed. An mRNA without a stop codon leads to an incorrectly enlarged protein during translation, which can no longer assume the protein folding that is necessary for its function or can no longer fulfill other functions.

The two yeast ribosome subunits, named after their respective sedimentation coefficients 40S and 60S, separate from each other in the case of mRNA without a stop codon. The two proteins Ltn1p and Rqc2p then bind to the separated 60S subunit of the ribosome. Rqc2p binds alanine and threonine- laden tRNA to the 60S subunit of the ribosome, as a result of which a random alanine-threonine sequence is added to the C terminus of the resulting protein.

Ltn1p binds to the protein and leads to ubiquitinylation of the faulty protein. The protein labeled with ubiquitin is then broken down in the proteasome . Ltn1p is an E3 ubiquitin ligase and causes the last transfer step from ubiquitin to a protein, which is thereby marked for degradation . Ltn1p binds near the E (exit) site of the ribosome. In this case, a protein takes on the role of a template for protein synthesis, instead of the mRNA that is otherwise used.

Cell cycle

Similar to heat shock proteins , which act as chaperones to help other proteins fold , Rqc2p regulates the cell cycle in the event of excessive heat, cold or oxidative stress. Rqc2p signals to the cell that more heat shock proteins are required.

Web links

Individual evidence

↑ YJ Choe, SH Park, T. Hassemer, R. Körner, L. Vincenz-Donnelly, M. Hayer-Hartl, FU Hartl: Failure of RQC machinery causes protein aggregation and proteotoxic stress. In: Nature. Volume 531, number 7593, March 2016, pp. 191-195, doi : 10.1038 / nature16973 , PMID 26934223 .
↑ ^a ^b P.S. Shen, J. Park, Y. Qin, X. Li, K. Parsawar, MH Larson, J. Cox, Y. Cheng, AM Lambowitz, JS Weissman, O. Brandman, A. Frost: Protein synthesis. Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains. In: Science. Volume 347, number 6217, January 2015, pp. 75–78, doi : 10.1126 / science.1259724 , PMID 25554787 , PMC 4451101 (free full text).
↑ Ferruccio Ritossa: Discovery of the heat shock response . In: Cell Stress & Chaperones . tape 1 , no. 2 , June 1, 1996, ISSN 1355-8145 , p. 97-98 , PMID 9222594 , PMC 248460 (free full text).

[1] YJ Choe, SH Park, T. Hassemer, R. Körner, L. Vincenz-Donnelly, M. Hayer-Hartl, FU Hartl: Failure of RQC machinery causes protein aggregation and proteotoxic stress. In: Nature. Volume 531, number 7593, March 2016, pp. 191-195, doi : 10.1038 / nature16973 , PMID 26934223 .

[Shen-2] P.S. Shen, J. Park, Y. Qin, X. Li, K. Parsawar, MH Larson, J. Cox, Y. Cheng, AM Lambowitz, JS Weissman, O. Brandman, A. Frost: Protein synthesis. Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains. In: Science. Volume 347, number 6217, January 2015, pp. 75–78, doi : 10.1126 / science.1259724 , PMID 25554787 , PMC 4451101 (free full text).

[3] Ferruccio Ritossa: Discovery of the heat shock response . In: Cell Stress & Chaperones . tape 1 , no. 2 , June 1, 1996, ISSN 1355-8145 , p. 97-98 , PMID 9222594 , PMC 248460 (free full text).