Substrate specificity and the effect of calcium on Trypanosoma brucei metacaspase 2. (16th April 2013)

• Record Type: Journal Article
• Authors: Machado, Maurício F. M.; Marcondes, Marcelo F.; Juliano, Maria A.; McLuskey, Karen; Mottram, Jeremy C.; Moss, Catherine X.; Juliano, Luiz; Oliveira, Vitor
• Is Part Of: FEBS journal. Volume 280:Number 11(2013)
• Page Start: 2608
• Page End: 2621
• Publication Date: 2013-04-16
• Subjects: Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.12248
• Languages: English
• ISSNs: 1742-464X

Abstract

<abstract abstract-type="main" xml:lang="en" id="febs12248-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Metacaspases are cysteine peptidases found only in yeast, plants and lower eukaryotes, including the protozoa. To investigate the extended substrate specificity and effects of Ca<sup>2+</sup> on the activation of these enzymes, detailed kinetic, biochemical and structural analyses were carried out on metacaspase 2 from <italic>Trypanosoma brucei</italic> (TbMCA2). These results reveal that TbMCA2 has an unambiguous preference for basic amino acids at the P<sub>1</sub> position of peptide substrates and that this is most probably a result of hydrogen bonding from the P<sub>1</sub> residue to Asp95 and Asp211 in TbMCA2. In addition, TbMCA2 also has a preference for charged residues at the P<sub>2</sub> and P<sub>3</sub> positions and for small residues at the prime side of a peptide substrate. Studies into the effects of Ca<sup>2+</sup> on the enzyme revealed the presence of two Ca<sup>2+</sup> binding sites and a reversible structural modification of the enzyme upon Ca<sup>2+</sup> binding. In addition, the concentration of Ca<sup>2+</sup> used for activation of TbMCA2 was found to produce a differential effect on the activity of TbMCA2, but only when a series of peptides that differed in P<sub>2</sub> were examined, suggesting that Ca<sup>2+</sup> activation of TbMCA2 has a structural effect on the enzyme in the vicinity of the S<sub>2</sub> binding pocket. Collectively, these data give new insights into the substrate specificity and Ca<sup>2+</sup> activation of TbMCA2. This provides important functional details and leads to a better understanding of metacaspases, which are known to play an important role in trypanosomes and make attractive drug targets due to their absence in humans.</p> </abstract>