Differential Effects of Replacing Escherichia coli Ribosomal Protein L27 with Its Homologue from Aquifex aeolicus

AUTOR(ES)

Maguire, Bruce A.

FONTE

American Society for Microbiology

RESUMO

The rpmA gene, which encodes 50S ribosomal subunit protein L27, was cloned from the extreme thermophile Aquifex aeolicus, and the protein was overexpressed and purified. Comparison of the A. aeolicus protein with its homologue from Escherichia coli by circular dichroism analysis and proton nuclear magnetic resonance spectroscopy showed that it readily adopts some structure in solution that is very stable, whereas the E. coli protein is unstructured under the same conditions. A mutant of E. coli that lacks L27 was found earlier to be impaired in the assembly and function of the 50S subunit; both defects could be corrected by expression of E. coli L27 from an extrachromosomal copy of the rpmA gene. When A. aeolicus L27 was expressed in the same mutant, an increase in the growth rate occurred and the “foreign” L27 protein was incorporated into E. coli ribosomes. However, the presence of A. aeolicus L27 did not promote 50S subunit assembly. Thus, while the A. aeolicus protein can apparently replace its E. coli homologue functionally in completed ribosomes, it does not assist in the assembly of E. coli ribosomes that otherwise lack L27. Possible explanations for this paradoxical behavior are discussed.

Documentos Relacionados

• Nucleotide sequence of a cDNA encoding ribosomal protein L27 from Chlamydobotrys stellata.
• Ribosomal protein L27 is identical in chick and rat.
• Nucleotide sequence of four ribosomal protein L27 cDNAs from growing axillary buds of pea.
• Genes coding for ribosomal proteins S15, L21, and L27 map near argG in Escherichia coli.
• Aquifex aeolicus PilT, Homologue of a Surface Motility Protein, Is a Thermostable Oligomeric NTPase