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The unique structure of archaeal ‘hami’, highly complex cell appendages with nano‐grappling hooks
Author(s) -
Moissl Christine,
Rachel Reinhard,
Briegel Ariane,
Engelhardt Harald,
Huber Robert
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04294.x
Subject(s) - biology , appendage , protein filament , pilus , nanobiotechnology , adhesion , biophysics , electron microscope , microbiology and biotechnology , nanotechnology , biochemistry , anatomy , chemistry , materials science , escherichia coli , optics , organic chemistry , nanoparticle , gene , physics
Summary Proteinaceous, hair‐like appendages known as fimbriae or pili commonly extend from the surface of prokaryotic cells and serve important functions such as cell adhesion, biofilm formation, motility and DNA transfer. Here we show that a novel group of archaea from cold, sulphidic springs has developed cell surface appendages of an unexpectedly high complexity with a well‐defined base‐to‐top organization. It represents a new class of filamentous cell appendages, for which the term ‘hamus’ is proposed. Each archaeal cell is surrounded by a halo of about 100 hami, which mediate strong adhesion of the cells to surfaces of different chemical composition. The hami are mainly composed of 120 kDa subunits and remained stable in a broad temperature and pH range (0–70°C; 0.5–11.5). Electron microscopy and cryo‐electron tomography revealed that the hamus filament possesses a helical basic structure. At periodic distances, three prickles emanate from the filament, giving it the character of industrially produced barbwire. At its distal end the hami carry a tripartite, barbed grappling hook (60 nm in diameter). The architecture of this molecular hook is reminiscent of man‐made fishhooks, grapples and anchors. It appears that nature has developed a perfect mechanical nano‐tool in the course of biological evolution, which also might prove useful in the field of nanobiotechnology.