Biology subjects

Lindstrom, P. M.

Publications and source records attributed to Lindstrom, P. M..

3 recordsLinked to original sources

bioRxiv2026

Rescue of ribosomal protein bL27 in Streptococcus pneumoniae TIGR4 by an alternate protease

Streptococcus pneumoniae is a major human respiratory pathogen. The bacterial 70S ribosome is a target of many clinically important antibiotics. The N-terminus of ribosomal protein bL27 extends into the peptidyl transferase center and contributes to the translation process. In Firmicutes, full length bL27 contains an 8-12 amino acid N-terminal extension that is absent from Gram-negative bacteria. This extension is cleaved by the protease Prp, which is absent from organisms lacking the extension. Prp-mediated cleavage of bL27 is essential in Staphylococcus aureus, and Prp has been proposed as a potential antibiotic target. Here, we show that in S. pneumoniae strain TIGR4, a {Delta}prp mutant remained viable, and produced ribosomes containing cleaved bL27, whereas deletion of prp was not tolerated in strain D39. These results suggested the presence of an alternate bL27-processing protease in TIGR4 that was absent from D39. Using a combination of genomics, proteomics and biochemical analyses, we identified this enzyme as the product of previously uncharacterized gene SP_1145, encoding a protease that we named Ribosome rescue protease (Rrp). SP_1145 is carried on a mobile genetic element that is present in strain TIGR4, but absent from D39. Our findings shed light on an alternative mechanism for bL27 maturation, and indicate that some strains of S. pneumoniae harbor horizontally acquired redundant pathways for this essential ribosome processing step.

microbiology↗

bioRxiv2026

Formation and role of the portal of Staphylococcus aureus bacteriophage 80α

Bacteriophages play an important role in the pathogenicity of Staphylococcus aureus, an important human pathogen. Phages are involved in generalized and specialized transduction as well as a more specific process by which they mobilize elements known as phage-inducible chromosomal islands, of which S. aureus pathogenicity islands (SaPIs) are an important group. SaPIs are mobilized at high frequency through interactions with specific "helper" bacteriophages, such as 80, leading to packaging of the SaPI genomes into virions made from structural proteins supplied by the helper. Among these structural proteins is the portal protein, which forms a ring-like portal at a fivefold vertex of the capsid, through which the DNA is packaged during virion assembly and ejected upon infection of the host. We previously showed that portal protein expressed in E. coli forms tridecameric rings, while portals found in virions are always dodecamers. To understand the role of the portal in capsid assembly, DNA packaging and ejection, we have here examined this phenomenon further. We show that portals assembled at lower temperature form unclosed rings that may represent portal assembly intermediates. By analyzing portal protein deletion mutants, we demonstrate the involvement of the different functional domains in phage assembly and protein incorporation.

microbiology↗

bioRxiv2025

Cleavage of Streptococcus pneumoniae ribosomal protein L27 by the Prp protease

Streptococcus pneumoniae is one of the most important human respiratory pathogens worldwide. The increase in antibiotic resistance in S. pneumoniae and other pathogens is a significant public health concern. The streptococcal 70S ribosome is a prime target for antibiotics. Ribosomal protein L27 reaches into the peptidyl transferase center with its extended N-terminus and may be involved in the translation process. We have shown that L27 in Firmicutes, including staphylococci and streptococci, has an additional 9-12 amino acid N-terminal extension compared to Gram-negative organisms like Escherichia coli. The extension is cleaved by a protease called Prp that is absent from organisms that lack the extension. In S. aureus, Prp and the N-terminal extension of L27 are essential. Here, we have characterized the cleavage of L27 by Prp in S. pneumoniae. Prp forms dimers that efficiently cleave L27 in vitro. An inactive form of Prp (PrpC34S) binds to L27 without cleaving, whereas L27 with a mutation (F12A) of the cleavage site does not bind Prp. Overexpression of PrpC34S in vivo is detrimental to S. pneumoniae growth. Surprisingly, a S. pneumoniae {Delta}prp strain was viable, apparently due to cleavage of L27 by another, unknown protease. Unlike in S. aureus, a mutant strain lacking the N-terminal extension of L27 was viable, but showed impaired growth. Our study sheds light on a process that could be exploited for novel antibiotics, but emphasizes important differences between streptococci and staphylococci. HIGHLIGHTSO_LIRibosomal protein L27 in S. pneumoniae is N-terminally processed by Prp protease C_LIO_LIA S. pneumoniae {Delta}prp mutant is viable, but exhibits impaired growth C_LIO_LICleavage of L27 is required for viability, but the N-terminal extension is not essential C_LIO_LIIn the absence of Prp, L27 is processed by another protease. C_LIO_LIThere are distinct differences in the role of Prp between S. aureus and S. pneumoniae. C_LI

microbiology↗