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Rather than the familiar adaptive immune system based on immunoglobulin domains and major histocompatibility complex antigens common to mammals and most other vertebrates, jawless vertebrates such as lampreys and hagfish use modular units of leucine-rich repeat (LRR) proteins called “variable lymphocyte receptors” (VLRs) A and B.

Lampreys by Drow male, Wikimedia Commons

Neil Barclay, Oxford, this week reviewed a paper^[1] on the structure of VLRA in complex with a lysozyme ligand, which shows that VLRA can bind ‘antigen’ directly, without processing or antigen-presenting complexes, with nanomolar affinity. This strong affinity is achieved because multiple LRR repeats make multiple contacts with the ligand.

While we’re on structure, NMR gets a bit of bad press among crystallographers, for a number of reasons. But the report of the NMR solution structure of a seven helix transmembrane protein might garner the technique a little more respect^[2]. It’s incredibly difficult to do structural work on membrane proteins, but this opens up the whole world of G-protein-coupled receptors to a biophysical approach.

Ever wonder why it’s so difficult to wake up in the morning? A study on recovery from anaesthesia^[3] suggests that neural inertia may be to blame: the brain actually resists changing conscious states. This turns out to be important clinically, because dosage protocols for anaesthetics assume a symmetric effect