5emi
N-acetylmuramoyl-L-alanine amidase AmiC2 of Nostoc punctiforme
Structural highlights
FunctionPublication Abstract from PubMedTo orchestrate a complex life style in changing environments, the filamentous cyanobacterium Nostoc punctiforme facilitates communication between neighboring cells through septal junction complexes. This is achieved by nanopores that perforate the peptidoglycan (PGN) layer and traverse the cell septa. The N-acetylmuramoyl-L-alanine amidase AmiC2 in N. punctiforme (Npun_F1846) generates arrays of such nanopores in the septal PGN, in contrast to homologous amidases that mediate daughter cell separation after cell division in unicellular bacteria. Nanopore formation is therefore a novel property of AmiC homologs. Immunofluorescence shows that native AmiC2 localizes to the maturing septum. The high-resolution crystal structure (1.12 A) of its catalytic domain (AmiC2-cat) differs significantly from known structures of cell splitting and PGN recycling amidases. A wide and shallow binding cavity allows easy access of the substrate to the active site, which harbors an essential zinc ion. AmiC2-cat exhibits strong hydrolytic activity in vitro. A single point mutation of a conserved glutamate near the zinc ion results in total loss of activity, while zinc removal leads to instability of AmiC2-cat. An inhibitory alpha-helix, as found in the E. coli AmiC E. coli structure, is absent. Taken together, our data provide insight into the cell-biological, biochemical, and structural properties of an unusual cell wall lytic enzyme that generates nanopores for cell-cell communication in multicellular cyanobacteria. The novel structural features of the catalytic domain and the unique biological function of AmiC2 hint at mechanisms of action and regulation that are distinct from other amidases. This article is protected by copyright. All rights reserved. Enabling cell-cell communication via nanopore formation: structure, function, and localization of the unique cell wall amidase AmiC2 of Nostoc punctiforme.,Buttner FM, Faulhaber K, Forchhammer K, Maldener I, Stehle T FEBS J. 2016 Feb 1. doi: 10.1111/febs.13673. PMID:26833702[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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