Recombinant Salmonella paratyphi C Cardiolipin synthase (cls)

Basic Research Questions

• What is Salmonella paratyphi C Cardiolipin synthase (cls) and what is its function?

  Salmonella paratyphi C Cardiolipin synthase (cls) is an enzyme responsible for synthesizing cardiolipin, a crucial phospholipid component of bacterial membranes. This enzyme catalyzes the condensation of two phosphatidylglycerol molecules to form cardiolipin (CL) and glycerol. Cardiolipin is essential for proper membrane function and bacterial survival, particularly during stress conditions. In Salmonella species, there are three cardiolipin synthases (ClsA, ClsB, and ClsC), each with characteristic phospholipase-D motifs and specific functional roles during different growth phases . The gene encoding cls in Salmonella paratyphi C strain RKS4594 is identified as SPC_1989 with UniProt accession number C0Q393 .

• How do different cardiolipin synthase isoforms function in Salmonella species?

  Salmonella species possess three distinct cardiolipin synthases (ClsA, ClsB, and ClsC) with different substrate preferences and expression patterns:

  Isoform	Primary substrate	Expression pattern	Function
  ClsA	Two phosphatidylglycerol (PG) molecules	Predominant during logarithmic growth	Primary CL synthesis during active growth
  ClsB	Two PG molecules	Increased during stationary phase	Stress-responsive CL synthesis; can also synthesize phosphatidylglycerol, phosphatidylalcohols, phosphatidyltrehalose (PT), and diphosphatidyltrehalose (diPT)
  ClsC	One PG and one phosphatidylethanolamine (PE)	Activated during stationary phase and osmotic stress	Contributes to CL pool during stress conditions

  This functional redundancy likely allows for biochemical adaptation to various environmental conditions encountered during infection .

• What are the optimal storage conditions for recombinant Salmonella paratyphi C Cardiolipin synthase?

  For optimal stability and activity, recombinant Salmonella paratyphi C Cardiolipin synthase should be stored in a Tris-based buffer containing 50% glycerol at -20°C for regular use or at -80°C for extended storage. Working aliquots can be maintained at 4°C for up to one week. Repeated freezing and thawing should be avoided as this can lead to protein denaturation and loss of enzymatic activity . If lyophilized, the protein should be reconstituted in an appropriate buffer prior to use. For experimental work requiring multiple uses, it is recommended to create small working aliquots to minimize freeze-thaw cycles .

• What is the amino acid sequence and structural characteristics of Salmonella paratyphi C Cardiolipin synthase?

  The full-length Salmonella paratyphi C Cardiolipin synthase consists of 486 amino acids. The sequence begins with "MTTFYTVVSWLVILGYWVLIAGVTLRILMKRRAVPSAMAWLLIIYILPLVGIIAYLSVGE" and contains characteristic phospholipase-D motifs that are essential for its catalytic function . The protein has transmembrane domains that anchor it to the bacterial inner membrane, where it catalyzes cardiolipin synthesis. The enzyme contains conserved regions involved in substrate binding and catalysis, particularly the HxK(x)4D(x)6G(G/S)xN motif found in phospholipase D superfamily enzymes . Structural analysis reveals similarity to other bacterial cardiolipin synthases with a predicted molecular weight of approximately 53 kDa .

• How does cardiolipin content change during different growth phases in Salmonella?

  Cardiolipin content in Salmonella species varies significantly depending on growth phase. During exponential growth, cardiolipin comprises approximately 7% of total membrane phospholipids, with ClsA serving as the predominant synthase. Upon transition to stationary phase, the proportion increases to approximately 10%, with additional contributions from ClsB and ClsC . This growth phase-dependent regulation allows bacteria to adapt their membrane composition to changing environmental conditions. In stationary phase, the ClsC enzyme becomes particularly active, as demonstrated in studies where a clsA clsC double mutant completely lacked cardiolipin during stationary phase growth, whereas single clsA mutants still produced approximately 1% cardiolipin .

Advanced Research Questions