Aspergillus nidulans: One of the lesser known pathogen of the aspergilli group, A. nidulans is a model filamentous fungus widely used for studying eukaryotic cell biology (Galagan et al., 2005). A. nidulans possesses a phospholipid-hydrolyzing novel cPLA2 protein, PlaA, which shows maximum similarity to mammalian-type cPLA2 proteins (α, β, γ) (Hong et al., 2005). Like the three isoforms of human cPLA2 proteins, A. nidulans PlaA also consists of two separate catalytic domainsA and B, and possesses conserved residues (Gly-Gly-Gly-X-Arg and Gly-X-Ser-Gly-Ser motifs) in domain A that is essential for enzymatic activity (Hong et al., 2005). In addition, amino acid sequence of PlaA comprises of a putative N- terminal myristoylation site (Gly-Ser-Phe-His-Ser-Ser)
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Most of the sPLA2 enzymes possesses a catalytic center that has no catalytic Ser but contains a tightly bound water molecule that acts as a potential nucleophile (Verheij et al., 1980; Scott et al., 1990; Pickard et al., 1996). Majority of eukaryotic sPLA2 also have an N terminal signal peptide for secretion that is cleaved upon internalization into the endoplasmic reticulum or into the periplasm as in bacteria (Dennis et al., 2011; Cavazzini et al., 2013). Based on structural and functional properties, sPLA2 has been grouped into classes I, II, III, V, IX to XIII while cPLA2 is included in the remaining IV, VI, VII and VIII classes (Matoba et al., 2002). The sPLA2 enzymes were first identified in mammalian pancreatic juice and cobra venoms, and subsequently they were also widely discovered in reptiles, insects, plants, bacteria, viruses as well as fungi (Nakashima et al., 2003; Nevaleinen et al., 2011; 2013). This family of enzymes plays diverse roles in a wide range of organisms and tissues and are known to regulate a number of biological processes such as atherosclerosis, eicosanoid …show more content…
crassa is a well-known model filamentous fungus and contributed significantly in understanding numerous aspects of eukaryotic cell biology (Galagan et al., 2003). N. crassa comprises of two sPLA2 proteins encoded by NCU06650 and NCU09423 gene and their predicted primary structures possesses conserved residues similar to other microbial sPLA2 members of group XIV. The sPLA2 protein (186 amino acids) encoded by NCU06650 gene consists of a 19 amino acids long predicted N-terminal signal sequence and 4 Cys residues while NCU09423 (249 amino acids) encoded sPLA2 gene is comprised of a predicted signal sequence of 23 amino acids and 6 Cys residues (Barman and Tamuli, 2015; Takayanagi et al., 2015). Both the sPLA2s of N. crassa displays similar enzymatic properties with respect to Ca2+ requirement and pH preference, although they significantly differ with each other in terms of folding properties (Takayanagi et al., 2015). The N. crassa strains lacking splA2 displayed growth defects in response to increased [Ca2+]c induced by the Ca2+ionophore A23187, alterations in the carotenoid profile, and decreased survival after exposure to hydrogen peroxide induced oxidative stress and in induced thermotolerance (Barman and Tamuli, 2015). These phenotypes may result from a disruption in calcium homeostasis that suggested a possible role of splA2 in calcium signaling and regulation of homeostasis in N. crassa (Barman and Tamuli, 2015;
Most of the sPLA2 enzymes possesses a catalytic center that has no catalytic Ser but contains a tightly bound water molecule that acts as a potential nucleophile (Verheij et al., 1980; Scott et al., 1990; Pickard et al., 1996). Majority of eukaryotic sPLA2 also have an N terminal signal peptide for secretion that is cleaved upon internalization into the endoplasmic reticulum or into the periplasm as in bacteria (Dennis et al., 2011; Cavazzini et al., 2013). Based on structural and functional properties, sPLA2 has been grouped into classes I, II, III, V, IX to XIII while cPLA2 is included in the remaining IV, VI, VII and VIII classes (Matoba et al., 2002). The sPLA2 enzymes were first identified in mammalian pancreatic juice and cobra venoms, and subsequently they were also widely discovered in reptiles, insects, plants, bacteria, viruses as well as fungi (Nakashima et al., 2003; Nevaleinen et al., 2011; 2013). This family of enzymes plays diverse roles in a wide range of organisms and tissues and are known to regulate a number of biological processes such as atherosclerosis, eicosanoid …show more content…
crassa is a well-known model filamentous fungus and contributed significantly in understanding numerous aspects of eukaryotic cell biology (Galagan et al., 2003). N. crassa comprises of two sPLA2 proteins encoded by NCU06650 and NCU09423 gene and their predicted primary structures possesses conserved residues similar to other microbial sPLA2 members of group XIV. The sPLA2 protein (186 amino acids) encoded by NCU06650 gene consists of a 19 amino acids long predicted N-terminal signal sequence and 4 Cys residues while NCU09423 (249 amino acids) encoded sPLA2 gene is comprised of a predicted signal sequence of 23 amino acids and 6 Cys residues (Barman and Tamuli, 2015; Takayanagi et al., 2015). Both the sPLA2s of N. crassa displays similar enzymatic properties with respect to Ca2+ requirement and pH preference, although they significantly differ with each other in terms of folding properties (Takayanagi et al., 2015). The N. crassa strains lacking splA2 displayed growth defects in response to increased [Ca2+]c induced by the Ca2+ionophore A23187, alterations in the carotenoid profile, and decreased survival after exposure to hydrogen peroxide induced oxidative stress and in induced thermotolerance (Barman and Tamuli, 2015). These phenotypes may result from a disruption in calcium homeostasis that suggested a possible role of splA2 in calcium signaling and regulation of homeostasis in N. crassa (Barman and Tamuli, 2015;