Single-Domain Peptidyl-Prolylcis/transIsomerase FkpA from Corynebacterium glutamicum Improves the Biomass Yield at Increased Growth Temperatures
ABSTRACTPeptidyl-prolylcis/transisomerases (PPIases) catalyze the rate-limiting protein folding step at peptidyl bonds preceding proline residues and were found to be involved in several biological processes, including gene expression, signal transduction, and protein secretion. Representative enzymes were found in almost all sequenced genomes, includingCorynebacterium glutamicum, a facultative anaerobic Gram-positive and industrial workhorse for the production of amino acids. InC. glutamicum, a predicted single-domain FK-506 (tacrolimus) binding protein (FKBP)-type PPIase (FkpA) is encoded directly downstream ofgltA, which encodes citrate synthase (CS). This gene cluster is also present in otherActinobacteria. Here we carried outin vitroandin vivoexperiments to study the function and influence of predicted FkpA inC. glutamicum.In vitro, FkpA indeed shows typical PPIase activity with artificial substrates and is inhibited by FK-506. Furthermore, FkpA delays the aggregation of CS, which is also inhibited by FK-506. Surprisingly, FkpA has a positive effect on the activity and temperature range of CSin vitro. Deletion offkpAcauses a 50% reduced biomass yield compared to that of the wild type when grown at 37°C, whereas there is only a 10% reduced biomass yield at the optimal growth temperature of 30°C accompanied by accumulation of 7 mMl-glutamate and 22 mM 2-oxoglutarate. Thus, FkpA may be exploited for improved product formation in biotechnical processes. Comparative transcriptome analysis revealed 69 genes which exhibit ≥2-fold mRNA level changes inC. glutamicumΔfkpA, giving insight into the transcriptional response upon mild heat stress when FkpA is absent.