Insights on the participation of Glu256 and Asp204 in the oligomeric structure and cooperative effects of human arginase type I

[Display omitted] •Arginase has important biomedical functions in vascular diseases and asthma.•We analyzed new residues that participate in maintain the oligomeric state.•We analyzed residues relevant for cooperative properties.•Asp204 is relevant to maintain the oligomeric state of the enzyme.•Glu...

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Bibliographic Details
Published in:Journal of structural biology 2020-08, Vol.211 (2), p.107533-107533, Article 107533
Main Authors: Lobos, Marcela, Figueroa, Maximiliano, Martínez-Oyanedel, José, López, Vasthi, García-Robles, María de los Ángeles, Tarifeño-Saldivia, Estefanía, Carvajal, Nelson, Uribe, Elena
Format: Article
Language:English
Subjects:
Arginase
Arginine
Cooperativity
Oligomeric
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Summary:[Display omitted] •Arginase has important biomedical functions in vascular diseases and asthma.•We analyzed new residues that participate in maintain the oligomeric state.•We analyzed residues relevant for cooperative properties.•Asp204 is relevant to maintain the oligomeric state of the enzyme.•Glu256 residue participate in cooperative communication between subunits. Arginase (EC 3.5.3.1) catalyzes the hydrolysis of L-arginine to L-ornithine and urea, and requires a bivalent cation, especially Mn2+ for its catalytic activity. It is a component of the urea cycle and regulates the intracellular levels of l-arginine, which makes the arginase a target for treatment of vascular diseases and asthma. Mammalian arginases contain an unusual S-shaped motif located at the intermonomeric interface. Until now, the studies were limited to structural role of the motif. Then, our interest was focused on functional aspects and our hypothesis has been that the motif is essential for maintain the oligomeric state, having Arg308 as a central axis. Previously, we have shown that the R308A mutant is monomeric and re-associates to the trimeric-cooperative state in the presence of low concentrations of guanidine chloride. We have now mutated Asp204 that interacts with Arg308 in the neighbor subunit, and also we mutated Glu256, proposed as important for oligomerization. Concretely, the human arginase I mutants D204A, D204E, E256A, E256Q and E256D were generated and examined. No differences were observed in the kinetic parameters at pH 9.5 or in tryptophan fluorescence. However, the D204A and E256Q variants were monomeric. On the other hand, D204E and E256D proved to be trimeric and kinetically cooperative at pH 7.5, whereas hyperbolic kinetics was exhibited by E256A, also trimeric. The results obtained strongly support the importance of the interaction between Arg255 and Glu256 in the cooperative properties of arginase, and Asp204 would be relevant to maintain the oligomeric state through salt bridges with Arg255 and Arg308.
ISSN:1047-8477
1095-8657
DOI:10.1016/j.jsb.2020.107533