A diadenosine 5',5''-P1P4 tetraphosphate (Ap4A) hydrolase from Arabidopsis thaliana that is activated preferentially by Mn2+ ions.

Abstract

Asymmetrical diadenosine 5',5''-P(1)P(4) tetraphosphate (Ap(4)A) hydrolases are key enzymes controlling the in vivo concentration of Ap(4)A--an important signaling molecule involved in regulation of DNA replication and repair, signaling in stress response and apoptosis. Sequence homologies indicate that the genome of the model plant Arabidopsis thaliana contains at least three open reading frames encoding presumptive Ap(4)A hydrolases: At1g30110, At3g10620, and At5g06340. In this work we present efficient overexpression and detailed biochemical characteristics of the AtNUDX25 protein encoded by the At1g30110 gene. Aided by the determination of the binding constants of Mn(Ap(4)A) and Mg(Ap(4)A) complexes using isothermal titration calorimetry (ITC) we show that AtNUDX25 preferentially hydrolyzes Ap(4)A in the form of a Mn(2+) complex.

Chlamydia trachomatisCT771 (nudH) Is an Asymmetric Ap4A Hydrolase

“…Furthermore, enzymatic analyses did confirm Ap 4 A hydrolase activity for CT771 and reveal an intriguing inverse relationship between concentration and the preferred divalent cation. While the majority of Ap 4 A hydrolases preferentially utilize Mg 2+ , instances of maximal activity in the presence of Mn 2+ have been previously documented . Furthermore, in the presence of Mn 2+ the K m value for Ap 4 A was roughly 2 orders of magnitude tighter than that in the presence of Mg 2+ for CT771, yet increasing concentrations of Mn 2+ resulted in a decreased catalytic rate and efficiency (Table ).…”

Quantification of mRNA and protein and integration with protein turnover in a bacterium

“…Proteins upregulated in response to heat shock include the chaperons DnaK (+18%), GroES (+29%) and the proteases ClpB (+65%) and Lon (+28%), indicating a concerted response involving re-folding and degradation of heat-damaged proteins. Following mitomycin-induced DNA damage; we observed a doubling of Hit1, an important signalling molecule involved in regulation of DNA replication and repair ( Szurmak et al, 2008 ). Osmotic stress led to only moderate abundance changes in the proteome, including 16 proteins with abundance changes unique to this stress ( Figure 1C ; Supplementary Table S3 ).…”

Manganese in Plants: From Acquisition to Subcellular Allocation

“…In addition, Mn plays a role in such diverse processes as chloroplast development (Rohdich et al, 2000;Hsieh et al, 2008), purine and urea catabolism (Werner et al, 2008;Cao et al, 2010), phospholipid biosynthesis (Collin et al, 1999;Nowicki et al, 2005), Ca 2+ signaling (Kim et al, 2003;Hashimoto et al, 2012), DNA repair (Takahashi et al, 2007;Szurmak et al, 2008), or histidine biosynthesis (Glynn et al, 2005).…”