Proteins are the essential building blocks of our bodies, encoded by our genes to carry out all manner of tasks. Within our cells, they are made in a network of interconnecting membranes called the rough endoplasmic reticulum (ER), to which are attached cellular factories that assemble proteins from amino acids. Recent images of the ER, taken using electron microscopy, have yielded new insights into its structure. Working on mouse salivary gland cells, which secrete vast amounts of proteins to produce saliva, researchers assembled multiple images of thin sections through the ER to build the three-dimensional model shown above. It reveals that stacks of membranes are linked by curving, helix-like connections, resembling the ramps between levels in a multi-storey car park. This arrangement maximises the amount of membrane surface that can be packed into a small cell, so enabling the synthesis of all the necessary proteins at the same time.
Written by Emmanuelle Briolat
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