Jeffrey Kendall Brown, Ph.D.


Biological Sciences 2012

Area of Doctoral Study: Biological Sciences
Undergraduate Institute: East Carolina University
Graduate Institute: Johns Hopkins University (M.S.)

Research Advisor:  Lasse Lindahl, Ph.D.

Current Position: Military Assignment, Walter Reed Army Institute of Research

Description of Research

Analyses of assembly, structural, and functional defects in the ribosome of L4 and L22 mutant Escherichia coli strains

 The ribosome is a complex macromolecule responsible for translation of the genetic code and protein synthesis. The ribosome has two unequal subunits of which the larger one contains the peptidyl transferase center (PTC), the enzymatic activity that forms peptide bonds.  A  100 Å long tunnel from the PTC to the cytoplasm serves as a conduit for transport of nascent peptides to the cytoplasm or membrane translocon.  The tips of the extended loops (also called tentacles) of two proteins, L4 and L22, contribute to the surface of the narrowest portion of Escherichia coli’s exit tunnel. Previous researchers in the Lindahl-Zengel lab have identified mutations in the tentacles of these proteins which bestow resistance to a class of antibiotics referred to as macrolides. Although these mutants have the advantage of growing in the presence of the antibiotic, erythromycin, they have the disadvantage of growing slower than the wildtype. The decreased growth rate may be caused by structural changes within the 23S component of the large subunit induced by non-optimal interactions between the mutant proteins and the rRNA. This in turn could affect ribosomal assembly and ultimately reduce the catalytic activity in the PTC. My proposal involves estimating to which degree the reduced cell growth rate can be attributed  to (i) the rate of the peptide bond formation in the peptidyltransferase center, and (ii) the reduced rate of the ribosomal assembly. The objective of my research is to conduct functional, structural and assembly analyses within the ribosome’s large subunit of E. coli, which contains mutations within the L4 or L22 proteins.