All cells — bacterial or human — secrete up to 10 or 20 percent of the proteins that they make. Human secreted proteins, for example, include components of serum, hormones, growth factors that promote cell development during embryogenesis and tissue remodeling, and proteins that provide the basis for immune cell signaling during infection or when fighting cancer. The secretion process, however, isn't an easy feat for cells, as they need to move the proteins across a membrane through a channel. Transport requires the formation of a hairpin, formed by an initiator protein. In a recent study, Don Oliver, the Daniel Ayres Professor…