Cystathionine β-Synthase (CBS) Domain-containing Pyrophosphatase as a Target for Diadenosine Polyphosphates in Bacteria

Abstract

Background: Many soluble pyrophosphatases contain two regulatory nucleotide-binding CBS domains with or without an intercalating DRTGG domain. Results: Linear P

The Tetrameric Structure of Nucleotide-regulated Pyrophosphatase and Its Modulation by Deletion Mutagenesis and Ligand Binding

“…This co-operativity clearly results from interactions within the pairs of the regulatory parts of monomers 1-3 and 2-4, but not between these pairs because they lie far apart in CBS-PPase tetramer. This interpretation is consistent with the non-cooperative binding of adenosine polyphosphates that demonstrated a stoichiometry of one per two monomers [14] because each molecule of this ligand occupies both regulatory sites in each of the two distant monomer pairs [12]. Dilution-induced dissociation of CBS-PPase apparently yields dimers 1-3 and 2-4, which are inactive because the DHH domains cannot form the catalytically competent association via extended β-sheet.…”

“…Three of these PPases contain the full set of domains (DHH, DHHA2, DRTGG, and two copies of CBS), and the remaining two lack the DRTGG domain. Both CBS-PPase types are regulated by monoadenosine phosphates (AMP, ADP, and ATP) that bind to CBS domains, but only the former type is activated by diadenosine polyphosphates [14], important cellular alarmons [23]. Most other reported PPases are homohexamers of approximately 20-kDa subunits (prokaryotic Family I), homodimers of 32-70-kDa subunits (eukaryotic Family I, prokaryotic canonical Family II, and cation-transporting membrane PPases), or monomers (Family III).…”

“…Kinetic co-operativity (decreased Km value for interaction with the second substrate molecule) [13] apparently results from interactions in pairs of monomers 1-2 and 3-4, as only this type of interaction occurs in co-operative dimeric Family II PPases devoid of the regulatory CBS domains [28]. AMP, ADP, and ATP are bound by CBS-PPase co-operatively with a stoichiometry of one per monomer [14]. This co-operativity clearly results from interactions within the pairs of the regulatory parts of monomers 1-3 and 2-4, but not between these pairs because they lie far apart in CBS-PPase tetramer.…”

“…1B,C) [11,12]. CBS-PPases are unique among different PPases in being differentially regulated (activated or inhibited) by adenine mono-and dinucleotides that bind to the CBS domains [11,13,14]. This property is thought to enhance the control of PPi level under stress conditions and, hence, the viability of the bacterial host [14].…”

“…CBS-PPases are unique among different PPases in being differentially regulated (activated or inhibited) by adenine mono-and dinucleotides that bind to the CBS domains [11,13,14]. This property is thought to enhance the control of PPi level under stress conditions and, hence, the viability of the bacterial host [14]. The regulating nucleotides bind to the enzyme in a positively co-operative manner [13], a phenomenon associated with the oligomeric structure of CBS-PPase.…”