title: Genetic Analysis of the Lambda Spanins Rz and Rz1: Identification of Functional Domains.
abstract: Coliphage lambda proteins Rz and Rz1 are the inner membrane and outer membrane subunits of the spanin complex-a heterotetramer that bridges the periplasm and is essential for the disruption of the outer membrane during phage lysis. Recent evidence suggests the spanin complex functions by fusing the inner and outer membrane. Here, we use a genetics approach to investigate and characterize determinants of spanin function. BecauseRz1is entirely embedded in the +1 reading frame ofRz, the genes were disembedded before using random mutagenesis to construct a library of lysis-defective alleles for both genes. Surprisingly, most of the lysis-defective missense mutants exhibited normal accumulation or localizationin vivo, and also were found to be normal for complex formationin vitroAnalysis of the distribution and nature of single missense mutations revealed subdomains that resemble key motifs in established membrane-fusion systems,i.e., two coiled-coil domains in Rz, a proline-rich region of Rz1, and flexible linkers in both proteins. When coding sequences are aligned respective to the embedded genetic architecture ofRz1withinRz, genetically silent domains ofRz1correspond to mutationally sensitive domains inRz, and vice versa, suggesting that the modular structure of the two subunits facilitated the evolutionary compression that resulted in the unique embedded gene architecture.
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Jesse
authors.identifier: 0000-0001-8387-9273
authors.initials: J
authors.lastname: Cahill
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Manoj
authors.initials: M
authors.lastname: Rajaure
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Chandler
authors.initials: C
authors.lastname: O'Leary
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Jordan
authors.initials: J
authors.lastname: Sloan
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Armando
authors.initials: A
authors.lastname: Marrufo
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Ashley
authors.initials: A
authors.lastname: Holt
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Aneesha
authors.initials: A
authors.lastname: Kulkarni
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
authors.forename: Oscar
authors.initials: O
authors.lastname: Hernandez
authors.affiliation: Center for Phage Technology and Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843 ryland@tamu.edu.
authors.forename: Ry
authors.initials: R
authors.lastname: Young
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D010582:Bacteriophage lambda / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000821:virology; D029968:Escherichia coli Proteins / Q000235:genetics; D008561:Membrane Fusion / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D009154:Mutation; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D014764:Viral Proteins; C043426:inner membrane protein, E coli; C082268:Rz protein, bacteriophage lambda
keywords: Escherichia coli; lysis; membrane fusion; phage