Membrane protein crystallography – is it still a fine art?


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Membrane proteins serve a number of vital roles in the body, including oxygen production, transport of nutrients into cells, transport of water into and out of cells, removal of waste products, and allowing information to enter cells. Thirty percent of genes in the human genome encode for membrane proteins and 60% of drug targets are membrane proteins. Mutations or improper folding of membrane proteins are associated with many known diseases, such as heart disease, depression, obesity, and cancer. Dr. Isabel Moraes, Head of the Membrane Protein Laboratory (MPL) at Diamond Light Source (DLS), UK, has recently reviewed the methods used for the successful crystallization of membrane proteins, summarized in our latest labCrystal journal.

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Fig 1: Dr Isabel Moraes working with SPT Labtech’s mosquito®  LCP

Bottlenecks in membrane protein structure determination

In the last decade significant efforts have been made to improve the production and crystallization of membrane proteins. Many of the crystallization strategies have benefited from developments in automation and miniaturization. For example, the use of liquid handling robots such as SPT Labtech’s mosquito® range has increased the number of potential crystallization conditions that can be screened while at the same time reducing the amount of protein sample required.

In our new edition of labCrystal you can read about Dr. Moraes’ latest work on the crystallization of anti-histamine drug targets. Dr. Moraes remarked, “In our lab, 99% of the solved membrane protein structures are from crystals set up with our SPT Labtech mosquito® LCP.”

Lipdic cubic phase technology miniaturized

In addition to the vapor diffusion method, membrane proteins are often crystallized in lipidic cubic phase (LCP). SPT Labtech’s mosquito LCP provides the combination of three important factors to Dr. Moraes’ team for successful crystallization;

1) miniaturization – volumes can be reduced to nanolitre ranges (as low as 25 nL)

2) speed – rapid dispensing of a 96-well LCP plate to about 4 mins

3) accuracy –  improved reproducibility with more accurate dispensing

Due to the fast set-up time, evaporation is reduced. However, SPT Labtech’s active humidity chamber is routinely used to avoid any possibility of drop evaporation.

Dr Moraes commented on the robustness of the mosquito® LCP in a multi-user environment, “Because we operate as a user facility and have many different external scientists working in the lab, we really need a crystallization machine that it is easy to work with and reliable….that’s our mosquito®! I have been using several generations of the mosquito® for more than 8 years and it has never let me down!”