scholarly journals Mechanistic Insights into the Allosteric Regulation of the Clr4 Protein Lysine Methyltransferase by Autoinhibition and Automethylation

2020 ◽  
Vol 21 (22) ◽  
pp. 8832
Author(s):  
Mina S. Khella ◽  
Alexander Bröhm ◽  
Sara Weirich ◽  
Albert Jeltsch
Keyword(s):  
Active Site ◽  
Histone H3 ◽  
Enzyme Activation ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Structural Studies ◽  
Peptide Substrates ◽  
Heterochromatin Formation ◽  
Lysine Residues ◽  
Lysine Methyltransferase

Clr4 is a histone H3 lysine 9 methyltransferase in Schizosaccharomyces pombe that is essential for heterochromatin formation. Previous biochemical and structural studies have shown that Clr4 is in an autoinhibited state in which an autoregulatory loop (ARL) blocks the active site. Automethylation of lysine residues in the ARL relieves autoinhibition. To investigate the mechanism of Clr4 regulation by autoinhibition and automethylation, we exchanged residues in the ARL by site-directed mutagenesis leading to stimulation or inhibition of automethylation and corresponding changes in Clr4 catalytic activity. Furthermore, we demonstrate that Clr4 prefers monomethylated (H3K9me1) over unmodified (H3K9me0) histone peptide substrates, similar to related human enzymes and, accordingly, H3K9me1 is more efficient in overcoming autoinhibition. Due to enzyme activation by automethylation, we observed a sigmoidal dependence of Clr4 activity on the AdoMet concentration, with stimulation at high AdoMet levels. In contrast, an automethylation-deficient mutant showed a hyperbolic Michaelis–Menten type relationship. These data suggest that automethylation of the ARL could act as a sensor for AdoMet levels in cells and regulate the generation and maintenance of heterochromatin accordingly. This process could connect epigenome modifications with the metabolic state of cells. As other human protein lysine methyltransferases (for example, PRC2) also use automethylation/autoinhibition mechanisms, our results may provide a model to describe their regulation as well.

scholarly journals Inhibition of rabbit muscle aldolase by phosphorylated aromatic compounds

1997 ◽  
Vol 323 (1) ◽  
pp. 71-77 ◽  
Author(s):  
Casimir BLONSKI ◽  
Danielle DE MOISSAC ◽  
Jacques PÉRIÉ ◽  
Jurgen SYGUSCH
Keyword(s):  
Schiff Base ◽  
Active Site ◽  
Enzyme Inactivation ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Rabbit Muscle ◽  
Lysine Residues ◽  
Schiff Base Formation ◽  
Fructose 1,6 Bisphosphate ◽  
Base Formation

The interactions of the phosphorylated derivatives of hydroquinone (HQN-P2), resorcinol (RSN-P2), 4-hydroxybenzaldehyde (HBA-P) and 2,4-dihydroxybenzaldehyde (DHBA-P; phosphate group at position 4) with fructose bisphosphate aldolase were analysed by enzyme kinetics, UV/visible difference spectroscopy and site-directed mutagenesis. Enzyme activity was competitively inhibited in the presence of HQN-P2, RSN-P2 and HBA-P, whereas DHBA-P exhibited slow-binding inhibition. Inhibition by DHBA-P involved active-site Schiff-base formation and required a phenol group ortho to the aldehyde moiety. Rates of enzyme inactivation and of Schiff-base formation by DHBA-P were identical, and corresponded to 3.2-3.5 DHBA-P molecules covalently bound per aldolase tetramer at maximal inactivation. Site-directed mutagenesis of the active-site lysine residues at positions 107, 146 and 229 was found to be consistent with Schiff-base formation between DHBA-P and Lys-146, and this was promoted by Lys-229. Mutation of Glu-187, located vicinally between Lys-146 and Lys-229 in the active site, perturbed the rate of Schiff-base formation, suggesting a functional role for Glu-187 in Schiff-base formation and stabilization. The decreased cleavage activity of the active-site mutants towards fructose 1,6-bisphosphate is consistent with a proton-transfer mechanism involving Lys-229, Glu-187 and Lys-146.

scholarly journals Function of the 90-loop (Thr90–Glu100) region of staphylokinase in plasminogen activation probed through site-directed mutagenesis and loop deletion

2002 ◽  
Vol 365 (2) ◽  
pp. 379-389 ◽  
Author(s):  
Govindan RAJAMOHAN ◽  
Monika DAHIYA ◽  
Shekhar C. MANDE ◽  
Kanak L. DIKSHIT
Keyword(s):  
Active Site ◽  
Complex Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Kringle Domains ◽  
Lysine Residues ◽  
Modelling Studies ◽  
Activator Complex

Staphylokinsae (SAK) forms a bimolecular complex with human plasmin(ogen) and changes its substrate specificity by exposing new exosites that enhances accession of substrate plasminogen (PG) to the plasmin (Pm) active site. Protein modelling studies indicated the crucial role of a loop in SAK (SAK 90-loop; Thr90—Glu100) for the docking of the substrate PG to the SAK—Pm complex. Function of SAK 90-loop was studied by site-directed mutagenesis and loop deletion. Deletion of nine amino acid residues (Tyr92—Glu100) from the SAK 90-loop, resulted in ≈60% reduction in the PG activation, but it retained the ability to generate an active site within the complex of loop mutant of SAK (SAKΔ90) and Pm. The preformed activator complex of SAKΔ90 with Pm, however, displayed a 50–60% reduction in substrate PG activation that remained unaffected in the presence of kringle domains (K1+K2+K3+K4) of PG, whereas PG activation by SAK—Pm complex displayed ∼50% reduction in the presence of kringles, suggesting the involvement of the kringle domains in modulating the PG activation by native SAK but not by SAKΔ90. Lysine residues (Lys94, Lys96, Lys97 and Lys98) of the SAK 90-loop were individually mutated into alanine and, among these four SAK loop mutants, SAKK97A and SAKK98A exhibited specific activities about one-third and one-quarter respectively of the native SAK. The kinetic parameters of PG activation of their 1:1 complex with Pm indicated that the Km values of PG towards the activator complex of these two SAK mutants were 4–6-fold higher, suggesting the decreased accessibility of the substrate PG to the activator complex formed by these SAK mutants. These results demonstrated the involvement of the Lys97 and Lys98 residues of the SAK 90-loop in assisting the interaction with substrate PG. These interactions of SAK—Pm activator complex via the SAK 90-loop may provide additional anchorage site(s) to the substrate PG that, in turn, may promote the overall process of SAK-mediated PG activation.

scholarly journals Threonine 57 is required for the post-translational activation ofEscherichia coliaspartate α-decarboxylase

2014 ◽  
Vol 70 (4) ◽  
pp. 1166-1172 ◽  
Author(s):  
Michael E. Webb ◽  
Briony A. Yorke ◽  
Tom Kershaw ◽  
Sarah Lovelock ◽  
Carina M. C. Lobley ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Active Site ◽  
Site Directed Mutagenesis ◽  
Intramolecular Rearrangement ◽  
Directed Mutagenesis ◽  
Vitamin B ◽  
Biosynthesis Pathway ◽  
Serine Residue ◽  
Translational Activation

Aspartate α-decarboxylase is a pyruvoyl-dependent decarboxylase required for the production of β-alanine in the bacterial pantothenate (vitamin B5) biosynthesis pathway. The pyruvoyl group is formedviathe intramolecular rearrangement of a serine residue to generate a backbone ester intermediate which is cleaved to generate an N-terminal pyruvoyl group. Site-directed mutagenesis of residues adjacent to the active site, including Tyr22, Thr57 and Tyr58, reveals that only mutation of Thr57 leads to changes in the degree of post-translational activation. The crystal structure of the site-directed mutant T57V is consistent with a non-rearranged backbone, supporting the hypothesis that Thr57 is required for the formation of the ester intermediate in activation.

Enzyme activity enhancement of chondroitinase ABC I from Proteus vulgaris by site-directed mutagenesis

RSC Advances ◽  
2015 ◽  
Vol 5 (93) ◽  
pp. 76040-76047 ◽  
Author(s):  
Zhenya Chen ◽  
Ye Li ◽  
Yue Feng ◽  
Liang Chen ◽  
Qipeng Yuan
Keyword(s):  
Active Site ◽  
Simulation Analysis ◽  
Docking Simulation ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Wild Type ◽  
Proteus Vulgaris ◽  
Molecular Docking Simulation ◽  
Activity Enhancement ◽  
First Time

Arg660 was found as a new active site and Asn795Ala and Trp818Ala mutants showed higher activities than the wild type based on molecular docking simulation analysis for the first time.

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