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Structure-function relationship of bacterial prolipoprotein diacylglyceryl transferase: functionally significant
1Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA.
Journal of Bacteriology
|December 1, 1995
Summary
Investigating bacterial prolipoprotein diacylglyceryl transferase (LGT) structure-function revealed conserved regions essential for activity. Mutations and chemical modification pinpointed key amino acids, aiding in understanding LGT enzyme mechanisms.
Area of Science:
- Molecular Biology
- Enzymology
- Bacterial Physiology
Background:
- Bacterial prolipoprotein diacylglyceryl transferase (LGT) is crucial for lipoprotein modification.
- Understanding LGT structure-function relationships is vital for bacterial cell envelope biogenesis.
- Previous studies have not fully elucidated the conserved regions and critical residues within LGT enzymes across diverse bacterial species.
Purpose of the Study:
- To investigate the structure-function relationship of bacterial LGT.
- To identify conserved amino acid sequences and essential residues within LGT enzymes.
- To analyze the impact of mutations and chemical modifications on LGT activity.
Main Methods:
- Comparative analysis of LGT primary structures from phylogenetically distant bacteria (E. coli, S. aureus, S. typhimurium, H. influenzae).
- Isolation and characterization of a Staphylococcus aureus LGT gene (lgt) by complementation of an E. coli mutant.
- Sequence analysis of wild-type and mutant LGT alleles, including site-directed mutagenesis and chemical modification studies (diethylpyrocarbonate).
- In vivo and in vitro assays to assess LGT activity.
Main Results:
- A Staphylococcus aureus LGT gene (lgt) was cloned and functionally expressed in E. coli, restoring prolipoprotein modification activity.
- Sequence analysis revealed conserved amino acid regions among LGT enzymes from different bacterial species, with a highly conserved H-GGLIG motif.
- Mutations within this conserved region (e.g., Gly-104 to Ser) resulted in temperature-sensitive growth and reduced LGT activity.
- Chemical modification with diethylpyrocarbonate inactivated E. coli LGT, suggesting the involvement of a His or Tyr residue in enzyme activity.
Conclusions:
- The study identified conserved structural elements and critical amino acid residues essential for bacterial LGT function.
- Mutational and chemical analyses provide insights into the catalytic mechanism and structure-function relationship of LGT.
- These findings contribute to a deeper understanding of lipoprotein modification in bacteria and potential targets for antimicrobial strategies.
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