Delta Lys120, a mutation which destabilizes the ribosome-binding domain of ribosomal protein L7/L12

Area of Science:

• Molecular Biology
• Ribosome Structure and Function
• Protein Engineering

Background:

• Ribosomal protein L7/L12 plays a crucial role in ribosome function.
• Understanding the structure-function relationship of L7/L12 is essential for deciphering protein synthesis mechanisms.

Purpose of the Study:

• To investigate the impact of deletions within ribosomal protein L7/L12 on mutant yields and ribosome binding.
• To determine the role of the C-terminal Lys120 in the stability and function of L7/L12 within the ribosome.

Main Methods:

• Site-directed mutagenesis was used to create five-residue deletions in L7/L12.
• Mutant genes were cloned into phage M13mp18 under the L10 promoter.
• Mutant yields were assessed, and ribosome binding properties were analyzed using S100 fractionation, LiCl washing, and ethanol extraction.

Main Results:

• Deletions near Ala63, Ala75, and Glu118 resulted in low mutant yields (<5%).
• Deletions of Glu118-Lys120 and Lys120 (L7/L12 delta Lys120) yielded higher mutant production (up to 50%).
• L7/L12 delta Lys120 exhibited altered ribosome extraction characteristics in ethanol-containing solvents, indicating destabilization of its binding domain.

Conclusions:

• The C-terminus of L7/L12, specifically Lys120, is critical for maintaining the protein's stable association with the ribosome.
• The delta Lys120 mutation destabilizes the ribosome-binding domain of L7/L12 in ethanol-containing solvents.
• Lys120 may be integral to the physiological ribosome-binding domain or essential for preserving its conformation under stress.