Marjorie Russel, Ph.D.
Adjunct Associate Professor
Russel’s research interests relate to how proteins and protein complexes are translocated across biological membranes in prokaryotes. More specifically, she studies how filamentous phage are assembled at the bacterial cytoplasmic membrane and extruded across the both cytoplasmic and outer membranes. She uses genetic, biochemical, physiological, and imaging techniques to determine the individual roles of phage-encoded proteins required for virion assembly and secretion. Taken together, this work has found that protein multimers in each membrane form a trans-envelope structure through which the assembling phage passes. It has identified two cytoplasmic membrane proteins which interact with host thioredoxin and a packing signal in the phage DNA and hydrolyze ATP. The outer membrane protein has a cylindrical structure composed of 14 identical subunits and forms a gated channel large enough to accommodate the phage. Furthermore, variants of this protein with mutations in the gate region cause the channel to open more frequently, thereby rendering bacteria highly sensitive to antibiotics. Homologous proteins encoded by pathogenic bacteria are components of secretion systems that export wide range of virulence factors, and significant functional and structural similarities between the phage and bacterial proteins suggest that findings in the former will be broadly applicable to bacterial pathogenesis.