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1.M.1 The Rz/Rz1 Spanin1 (Rz(1)) Family 

Bacteriophage lambda has four adjacent genes, S, R, Rz and Rz1, dedicated to host cell lysis. S encodes the holin and antiholin and R encodes the endolysin while Rz1 and Rz are an outer membrane lipoprotein (Rz1) and a type II signal anchor protein (Rz).  Together they comprise a spanin. The Rz-Rz1 complex spans the periplasm ane carries out the final step in the process of host lysis. Endolysin-mediated degradation of the cell wall is a prerequisite for conformational changes in the Rz-Rz1 complex leading to the juxtaposition and fusion of the two membranes. Fusion removes the last physical barrier to efficient release of progeny virions (Berry et al. 2008; Rajaure et al. 2015).  The lambda Rz and Rz1 lysis genes are remarkable in that Rz1, encoding the outer membrane lipoprotein, is completely embedded in the +1 register within Rz, which itself encodes the inner membrane protein (Summer et al. 2007; Berry et al. 2012; Berry et al. 2008; Kongari et al. 2018). 1.M.1.1 - 5 are most similar to the lambda phage i_spanin, 1.M.1.6 - 10 are derived from mycobacterial and gordonial phages and are most similar to each other, and 1.M.1.11 - 13 are derived from proteobacteria and are most similar to each other. These proteins are i-spanins. Only 1.M.1.1.1, 1.M.1.1.2 and 1.M.1.1.4 include both spanins (i-spanin and o-spanin) of the system.

References associated with 1.M.1 family:

Berry, J., E.J. Summer, D.K. Struck, and R. Young. (2008). The final step in the phage infection cycle: the Rz and Rz1 lysis proteins link the inner and outer membranes. Mol. Microbiol. 70: 341-351. 18713319
Berry, J., M. Rajaure, T. Pang, and R. Young. (2012). The spanin complex is essential for lambda lysis. J. Bacteriol. 194: 5667-5674. 22904283
Khakhum, N., U. Yordpratum, A. Boonmee, U. Tattawasart, J.L. Rodrigues, and R.W. Sermswan. (2016). Identification of the Burkholderia pseudomallei bacteriophage ST79 lysis gene cassette. J Appl Microbiol. [Epub: Ahead of Print] 27038077
Kongari, R., M. Rajaure, J. Cahill, E. Rasche, E. Mijalis, J. Berry, and R. Young. (2018). Phage spanins: diversity, topological dynamics and gene convergence. BMC Bioinformatics 19: 326. 30219026
Liu, P., X. Dong, X. Cao, Q. Xie, X. Huang, J. Jiang, H. Dai, Z. Tang, Y. Lin, S. Feng, and K. Luo. (2023). Identification of Three Campylobacter Lysins and Enhancement of Their Anti-Escherichia coli Efficacy Using Colicin-Based Translocation and Receptor-Binding Domain Fusion. Microbiol Spectr 11: e0451522. [Epub: Ahead of Print] 36749047
Rajaure, M., J. Berry, R. Kongari, J. Cahill, and R. Young. (2015). Membrane fusion during phage lysis. Proc. Natl. Acad. Sci. USA 112: 5497-5502. 25870259
Summer, E.J., J. Berry, T.A. Tran, L. Niu, D.K. Struck, and R. Young. (2007). Rz/Rz1 lysis gene equivalents in phages of Gram-negative hosts. J. Mol. Biol. 373: 1098-1112. 17900620