DNA binding to protein-gold nanocrystal conjugates

Area of Science:

• Biochemistry
• Nanotechnology
• Molecular Biology

Background:

• The lac repressor (LacI) is a crucial DNA-binding protein regulating gene expression in E. coli.
• Gold nanocrystals offer unique properties for bioconjugation and sensing applications.
• Understanding how conjugation affects protein function is vital for developing novel biosensors.

Purpose of the Study:

• To investigate the impact of gold nanocrystal conjugation on the DNA-binding activity of lac repressor (LacI).
• To engineer a modified LacI derivative (T334C) for oriented conjugation and assess its DNA-binding function.
• To determine the influence of conjugation strategies on the functional integrity of repressor-nanocrystal conjugates.

Main Methods:

• Development of LacI and T334C-gold nanocrystal conjugates.
• Analytical ultracentrifugation (AU) to characterize conjugate properties.
• Electrophoretic mobility shift assays (EMSA) to evaluate DNA binding to the O(1) operator sequence.

Main Results:

• Unmodified LacI conjugated to gold nanocrystals lost significant DNA-binding ability.
• The T334C derivative, designed for oriented conjugation, exhibited enhanced interaction with operator DNA when conjugated.
• The order of addition of components during conjugation critically affected the functionality of the resulting lac repressor conjugates.

Conclusions:

• Nonspecific conjugation of LacI to gold nanocrystals hinders DNA binding.
• Engineered derivatives like T334C can maintain or enhance DNA-binding function upon conjugation.
• Strategic control over the conjugation process is essential for creating functional protein-nanocrystal bioconjugates.