Glu-256 is a main structural determinant for oligomerisation of human arginase I.
One determinant that could play a role in the quaternary structure of human arginase is the pair of salt links between the strictly conserved residues R255 from one monomer and E256 from every adjacent subunit. In this work, the ionic interaction between monomers was disrupted by expressing a human arginase where Glu-256 had been substituted by Gln. Biochemical analyses of the mutant protein showed that: (i) it shares the wild-type kinetic parameters of the arginine substrate; (ii) E256Q arginase behaves as a monomer by gel filtration; (iii) it is drastically inactivated by dialysis in the presence of EDTA, an inhibitory effect which is reversed by addition of Mn(2+); and (iv) the mutant enzyme loses thermal stability. The lack of oligomerisation for E256Q arginase and the conservation of E256 throughout evolution of the protein family suggest that this residue is involved in the quaternary structure of arginases.
Sabio
G
G
Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain.
Mora
A
A
Rangel
M A
MA
Quesada
A
A
Marcos
C F
CF
Alonso
J C
JC
Soler
G
G
Centeno
F
F
D000595:Amino Acid Sequence; D001119:Arginase / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D018698:Glutamic Acid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011108:Polymers; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature
D004791:Enzyme Inhibitors; D011108:Polymers; D011994:Recombinant Proteins; D018698:Glutamic Acid; D008345:Manganese; D004492:Edetic Acid; D001119:Arginase