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Updated: Jan 19, 2026
Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery
Published on: August 6, 2019
Complete labelling of pneumococcal DNA-binding proteins with seleno-L-methionine
Fabián Lorenzo-Diaz1, Inmaculada Moreno-Córdoba2, Manuel Espinosa2
1Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna, Santa Cruz de Tenerife, Spain.
Abstract:
Streptococcus pneumoniae is a pathogenic and opportunistic Gram-positive bacterium that is the leading cause of community-acquired respiratory diseases, varying from mild- to deathly- infections. The appearance of antibiotic-resistant isolates has prompted the search for novel strategies and targets to tackle the bacterial resistances. One of the most promising approaches is the structure-based knowledge of possible targets in conjunction with rational design and docking of inhibitors of the chosen targets. A useful technique that helps to solve protein structures is to label them with an amino acid derivative like seleno-methionine that facilitates tracing of some of the amino acid residues. We have chosen two pneumococcal DNA-binding proteins, namely the relaxase domain of MobM protein from plasmid pMV158, and the RelB-RelE antitoxin-toxin protein complex. Through several changes that improve substantially a previous protocol (Budisa et al., 1995), we have used seleno-L-methionine to incorporate selenium into the amino acid sequence of the selected proteins. We have achieved 100% labelling of the proteins and could demonstrate that the labelled proteins retained full activity as judged from the relaxation of supercoiled plasmid DNA and from gel-retardation assays.
Insights
Researchers successfully incorporated selenium into Streptococcus pneumoniae DNA-binding proteins using seleno-L-methionine. The labeled proteins maintained full biological activity, aiding in structure-based drug design against antibiotic resistance.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- Streptococcus pneumoniae causes significant community-acquired respiratory infections.
- Antibiotic resistance in S. pneumoniae necessitates novel therapeutic strategies.
- Structure-based drug design requires detailed knowledge of protein targets.
Purpose of the Study:
- To develop an efficient method for labeling pneumococcal DNA-binding proteins with seleno-methionine.
- To assess the biological activity of seleno-methionine labeled proteins.
- To facilitate structure determination for drug discovery.
Main Methods:
- Incorporation of seleno-L-methionine into two S. pneumoniae DNA-binding proteins: MobM relaxase domain and RelB-RelE complex.
- Optimization of a previously established labeling protocol.
- Assays to confirm protein activity: DNA relaxation and gel-retardation.
Main Results:
- Achieved 100% seleno-methionine labeling of the target proteins.
- Demonstrated that labeled proteins retained full biological activity.
- Confirmed protein function through DNA relaxation and gel-retardation assays.
Conclusions:
- Seleno-methionine labeling is an effective method for studying S. pneumoniae DNA-binding proteins.
- Labeled proteins are suitable for structure-based drug design efforts.
- This approach aids in developing new strategies against antibiotic-resistant bacteria.
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