PerspectiveBiophysics

Membrane protein takes the brakes off

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Science  01 Feb 2019:
Vol. 363, Issue 6426, pp. 453-454
DOI: 10.1126/science.aaw2865

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Summary

Proteases are enzymes that use water to break amide bonds of protein substrates. This process—proteolysis—plays a myriad of roles from digestion to cell signaling, and regulation of protease functions are critical to all life forms. A fascinating class of proteases have their water-wielding active sites immersed in the water-repelling (hydrophobic) environment of the lipid bilayer and cleave the transmembrane regions of their substrates. How these intramembrane-cleaving proteases (I-CLiPs) (1) carry out this apparently paradoxical process has intrigued biochemists for 20 years. Among the challenges is deciphering how I-CLiPs diffuse through viscous cell membranes crowded with other membrane proteins to find their substrates. On page 497 of this issue, Kreutzberger et al. (2) find that one class of I-CLiPs, the rhomboid family, diffuses much faster than other membrane proteins, in violation of estimated speed limits for their size. This implies that these membrane proteins have evolved for rapid diffusion to carry out their functions effectively.

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