Lactococcus lactis YfiA is necessary and sufficient for ribosome dimerization

Abstract

SummaryDimerization and inactivation of ribosomes in Escherichia coli is a two-step process that involves the binding of ribosome modulation factor (RMF) and hibernation promotion factor (HPF). Lactococcus lactis MG1363 expresses a protein, YfiA Ll , which associates with ribosomes in the stationary phase of growth and is responsible for dimerization of ribosomes. We show that full-length YfiA Ll is necessary and sufficient for ribosome dimerization in L. lactis but also functions heterologously in vitro with E. coli ribosomes. Deletion of the yfiA gene has no effect on the growth rate but diminishes the survival of L. lactis under energy-starving conditions. The N-terminal domain of YfiA Ll is homologous to HPF from E. coli, whereas the C-terminal domain has no counterpart in E. coli. By assembling ribosome dimers in vitro, we could dissect the roles of the N-and C-terminal domains of YfiA Ll . It is concluded that the dimerization and inactivation of ribosomes in L. lactis and E. coli differ in several cellular and molecular aspects. In addition, two-dimensional maps of dimeric ribosomes from L. lactis obtained by single particle electron microscopy show a marked structural difference in monomer association in comparison to the ribosome dimers in E. coli.

The Listeria monocytogenes Hibernation-Promoting Factor Is Required for the Formation of 100S Ribosomes, Optimal Fitness, and Pathogenesis

“…E. coli ⌬rmf mutants display wildtype (WT) viability in culture for approximately 2 days and then die rapidly and yield 1,000-fold fewer CFU after 5 days of incubation (7). Similarly, RMF-deficient P. aeruginosa in deep layers of biofilms displays substantially reduced survival (42), and HPFdeficient L. lactis displays reduced survival and recovery from starvation (14). Despite being unable to form 100S ribosomes (similar to an E. coli RMF mutant), L. monocytogenes HPF mutants survived post-exponential-phase growth in monoculture comparably to the WT.…”

“…A recent report on hibernation in Bacillus subtilis established the importance of a long HPF homolog in 100S ribosome formation during amino acid starvation but did not discuss the functional importance of 100S ribosomes (16). The physiological consequences of hibernation in bacteria expressing long HPF have only recently begun to be elucidated, with the demonstration that L. lactis lacking HPF exhibits defects surviving and recovering from prolonged starvation (14). Transcription and/or translation of both rmf and hpf are upregulated at the entry to stationary phase (12,17).…”

“…The short and long forms of HPF produce distinct types of 100S ribosomes with different stabilities and temporal profiles (13). The long HPF bears a C-terminal extension that has been shown in Lactococcus lactis to contribute to ribosome dimerization in the same structural manner as RMF does in Gram-negative bacteria (14).…”

Long-Term Survival of Borrelia burgdorferi Lacking the Hibernation Promotion Factor Homolog in the Unfed Tick Vector

“…Overall, our secondary structure analyses of BB0449 did not detect large differences between HPF and BB0449 secondary structure, suggesting that BB0449 should be able to interact with ribosomes in B. burgdorferi. Biochemical studies, such as those performed previously in other bacteria (19,21,24,28,31,32,68), may help exclude the possibility of, or elucidate, a molecular role for BB0449 in B. burgdorferi ribosome modulation. Despite these caveats, the ability of B. burgdorferi totally lacking the BB0449 product to complete the mouse-tick infectious cycle, including spending approximately 9 months in unfed ticks, argues against a major impact on ribosome modulation by BB0449, if it exists.…”

“…There have been several other studies that used genetic techniques to address biological phenotypes of hpf-deficient strains. Deletion of hpf in E. coli, and of an hpf homolog in Lactococcus lactis, shows that the gene products are involved in ribosome dimerization, and mutants lacking HPF exhibited subtle effects on bacterial survival in E. coli and recovery of L. lactis following starvation (21,32). In addition, deletion of the Listeria monocytogenes hpf homolog eliminated ribosome dimerization and impaired tissue colonization in two mouse infection models (33), while deleting the hpf homolog in Erwinia amylovora, a plant pathogen, rendered this pathogen noninfectious to tobacco leaves and immature pear fruits (34).…”