Biology subjects

Zueckert, W. R.

Publications and source records attributed to Zueckert, W. R..

4 recordsLinked to original sources

bioRxiv2023

Quantitative analyses of interactions between SpoVG and RNA/DNA

1.The Borrelia burgdorferi SpoVG protein has previously been found to be a DNA- and RNA-binding protein. To aid in the elucidation of ligand motifs, affinities for numerous RNAs, ssDNAs, and dsDNAs were measured and compared. The loci used in the study were spoVG, glpFKD, erpAB, bb0242, flaB, and ospAB, with particular focus on the untranslated 5 portion of the mRNAs. Performing binding and competition assays yielded that the 5 end of spoVG mRNA had the highest affinity while the lowest observed affinity was to the 5 end of flaB mRNA. Mutagenesis studies of spoVG RNA and ssDNA sequences suggested that the formation of SpoVG-nucleic acid complexes are not entirely dependent on either sequence or structure. Additionally, exchanging uracil for thymine in ssDNAs did not affect protein-nucleic acid complex formation.

microbiology↗

bioRxiv2023

Borrelia burgdorferi PlzA is a c-di-GMP dependent DNA and RNA binding protein

The PilZ domain-containing protein, PlzA, is the only known cyclic di-GMP binding protein encoded by all Lyme disease spirochetes. PlzA has been implicated in the regulation of many borrelial processes, but the effector mechanism of PlzA was not previously known. Here we report that PlzA can bind DNA and RNA and that nucleic acid binding requires c-di-GMP, with the affinity of PlzA for nucleic acids increasing as concentrations of c-di-GMP were increased. A mutant PlzA that is incapable of binding c-di-GMP did not bind to any tested nucleic acids. We also determined that PlzA interacts predominantly with the major groove of DNA and that sequence length plays a role in DNA binding affinity. PlzA is a dual-domain protein with a PilZ-like N-terminal domain linked to a canonical C-terminal PilZ domain. Dissection of the domains demonstrated that the separated N-terminal domain bound nucleic acids independently of c-di-GMP. The C-terminal domain, which includes the c-di-GMP binding motifs, did not bind nucleic acids under any tested conditions. Our data are supported by computational docking, which predicts that c-di-GMP binding at the C-terminal domain stabilizes the overall protein structure and facilitates PlzA-DNA interactions via residues in the N-terminal domain. Based on our data, we propose that levels of c-di-GMP during the various stages of the enzootic life cycle direct PlzA binding to regulatory targets.

microbiology↗

bioRxiv2022

A Borrelia burgdorferi LptD Homolog Facilitates Flipping of Surface Lipoproteins Through the Spirochetal Outer Membrane

Borrelia spirochetes are unique among diderm bacteria in their lack of lipopolysaccharide (LPS) in the outer membrane (OM) and their abundance of surface-exposed lipoproteins with major roles in transmission, virulence, and pathogenesis. Despite their importance, little is known about how surface lipoproteins are translocated through the periplasm and the OM. In this study, we characterized Borrelia burgdorferi BB0838, a distant homolog of the OM LPS assembly protein LptD. Using a CRISPR interference approach, we showed that BB0838 is essential for cell growth. Upon BB0838 knockdown, sentinel surface lipoprotein OspA was retained in the inner leaflet of the OM, as determined by its inaccessibility to in situ proteolysis but its presence in OM vesicles. The secretion, insertion and topology of the B. burgdorferi OM porin P66 remained unaffected. MudPIT quantitative mass spectrometry analysis of the B. burgdorferi membrane-associated proteome further confirmed the selective periplasmic retention of surface lipoproteins under BB0838 knockdown conditions. Alphafold Multimer modeling predicted a B. burgdorferi LptB2FGCAD complex spanning the periplasm. Together, this indicates that BB0838 facilitates the essential terminal step in a distinctive spirochetal lipoprotein secretion pathway that evolved in parallel to the LPS secretion pathway in gram-negative bacteria. Hence, BB0838/LptDBb represents an attractive target for novel antimicrobials.

microbiology↗

bioRxiv2022

Inducible CRISPRi-based operon silencing and selective in trans gene complementation in Borrelia burgdorferi

To accelerate genetic studies on the Lyme disease pathogen Borrelia burgdorferi, we developed an enhanced CRISPR interference (CRISPRi) approach for IPTG-inducible repression of specific B. burgdorferi genes. The entire system is encoded on a compact 11-kb shuttle vector plasmid that allows for inducible expression of both the sgRNA module and a non-toxic codon-optimized dCas9 protein. We validated this CRISPRi system by targeting the genes encoding for OspA and OspB, abundant surface lipoproteins co-expressed by a single operon, and FlaB, the major subunit forming the periplasmic flagella. As in other systems, sgRNAs complementary to the non-template strand were consistently effective in gene repression, with 4- to 994-fold reductions in targeted transcript levels and concomitant reductions of in proteins levels. Furthermore, we showed that ospAB knockdowns could be selectively complemented in trans for OspA expression via the insertion of synonymous or non-synonymous CRISPRi-resistant PAM mutant (PAM*) ospA alleles into a unique site within the plasmid. Together, this establishes CRISPRi PAM* as a robust new genetic tool to simplify the study of B. burgdorferi genes, bypassing the need for gene disruptions by allelic exchange and avoiding rare-codon toxicity from heterologous expression of dCas9. SIGNIFICANCEBorrelia burgdorferi, the causative agent of Lyme disease, is a tick-borne pathogen of global importance. Here, we expand the genetic toolbox for studying B. burgdorferi physiology and pathogenesis by establishing a single-plasmid-based CRISPRi system with optional in trans complementation for the functional study of essential and non-essential proteins.

microbiology↗