Recombinant Prochlorococcus marinus subsp. pastoris 50S ribosomal protein L18 (rplR)

Basic Research Questions

• What is the function of 50S ribosomal protein L18 (rplR) in Prochlorococcus marinus?

  The 50S ribosomal protein L18 (rplR) in Prochlorococcus marinus is one of the critical proteins that binds and mediates the attachment of 5S RNA into the large ribosomal subunit, where it forms part of the central protuberance . Similar to its function in E. coli, PRPL18 interacts with both 23S rRNA and 5S rRNA , acting as a crucial link in the assembly of the 50S ribosomal subunit. This protein belongs to the universal ribosomal protein uL18 family and plays an essential role in ribosome biogenesis. Without functional rplR, the biogenesis of chloroplast ribosome would be defective, affecting intron splicing and potentially leading to impaired chloroplast development and function .

• How does strain variation affect rplR expression and function in different Prochlorococcus ecotypes?

  Prochlorococcus marinus exists as multiple ecotypes adapted to different light conditions, primarily categorized as high light (HL) and low light (LL) adapted strains . Gene expression analyses show that rplR and related ribosomal proteins may be differentially expressed based on environmental conditions and strain types. For instance, LL-adapted strains show pronounced strand-specific asymmetry in codon usage that is not observed in HL strains . Additionally, there are distinct dinucleotide abundance profiles exhibited by different strains:

  • LL strains with larger genomes and G+C content of approximately 50% (group LLa)

  • LL strains with reduced genomes and G+C content of approximately 35-37% (group LLb)

  • HL strains with their own distinct profiles

  These variations likely influence the expression and functional characteristics of rplR across different Prochlorococcus ecotypes, contributing to their specialized adaptations to various oceanic niches.

• What methods are recommended for reconstitution and storage of recombinant rplR?

  For optimal reconstitution of recombinant rplR from Prochlorococcus marinus:

  1. Briefly centrifuge the vial prior to opening to bring contents to the bottom

  2. Reconstitute the protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL

  3. Add glycerol to a final concentration of 5-50% (with 50% being commonly recommended)

  4. Aliquot for long-term storage at -20°C/-80°C

  The shelf life of reconstituted rplR is generally:

  • 6 months for liquid form at -20°C/-80°C

  • 12 months for lyophilized form at -20°C/-80°C

  Repeated freezing and thawing is not recommended. For short-term use, working aliquots can be stored at 4°C for up to one week .