In In the work reported here, we compare two physical-chemical characteristics, namely the interfacial compressibility and lateral organization (both influenced pronouncedly by cholesterol in mammalian cells) of squalene containing (total) and squalene devoid (polar) lipid extract of Halobacterium salinarum NRC-1. Pressure-area isotherms derived from Langmuir experiments map onto other classical amphiphiles and reveal packing characteristics and elastic compressibility properties to be strongly modulated by the presence of squalene in the total lipid extract: the incorporation of squalene dramatically extends elastic area compressibility and allows for tighter packing of archaeal lipid mixtures. Squalene also appears to influence lateral organization of archaeal membrane components. Epifluorescence and atomic force microscopy based characterization of Langmuir monolayers transferred onto solid hydrophilic reveal unusual domain morphology. Individual domains of microscopic dimensions (as well as their extended networks) exhibit a peculiar bowl-like topology as determined through atomic force microscopy.The presence of tall rims surrounding individual domains is consistent with the accumulation of squalene at the domain periphery, as well as a shift in isoprene chain orientation away from the substrate. Taken together, this evidence supports the notion that squalene has a role analogous to cholesterol in eukaryotic membranes, and that it might play a crucial role modulating chain order, lipid packing, and domain formation in the membranes of archaea.

Squalene's role in the formation and organization of membrane domains of <i>Halobacterium salinarum</i>

245th National Meeting (2013)

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Squalene's role in the formation and organization of membrane domains of Halobacterium salinarum