Open AccessThe PduQ Enzyme Is an Alcohol Dehydrogenase Used to Recycle NAD+ Internally within the Pdu Microcompartment of Salmonella enterica
Author(s) -
Sibo Cheng,
Chenguang Fan,
Sharmistha Sinha,
Thomas A. Bobik
Publication year - 2012
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0047144
Subject(s) - cofactor , nad+ kinase , alcohol dehydrogenase , biochemistry , salmonella enterica , enzyme , mutant , biology , isocitrate dehydrogenase , glycerol 3 phosphate dehydrogenase , chemistry , microbiology and biotechnology , escherichia coli , gene
Salmonella enterica uses a bacterial microcompartment (MCP) for coenzyme B 12 -dependent 1,2-propanediol (1,2-PD) utilization (Pdu). The Pdu MCP consists of a protein shell that encapsulates enzymes and cofactors required for metabolizing 1,2-PD as a carbon and energy source. Here we show that the PduQ protein of S. enterica is an iron-dependent alcohol dehydrogenase used for 1,2-PD catabolism. PduQ is also demonstrated to be a new component of the Pdu MCP. In addition, a series of in vivo and in vitro studies show that a primary function of PduQ is to recycle NADH to NAD + internally within the Pdu MCP in order to supply propionaldehyde dehydrogenase (PduP) with its required cofactor (NAD + ). Genetic tests determined that a pduQ deletion mutant grew slower than wild-type Salmonella on 1,2-PD and that this phenotype was not complemented by a non-MCP associated Adh2 from Zymomonas that catalyzes the same reaction. This suggests that PduQ has a MCP-specific function. We also found that a pduQ deletion mutant had no growth defect in a genetic background having a second mutation that prevents MCP formation which further supports a MCP-specific role for PduQ. Moreover, studies with purified Pdu MCPs demonstrated that the PduQ enzyme can convert NADH to NAD + to supply the PduP reaction in vitro. Cumulatively, these studies show that the PduQ enzyme is used to recycle NADH to NAD + internally within the Pdu MCP. To our knowledge, this is the first report of internal recycling as a mechanism for cofactor homeostasis within a bacterial MCP.