A symport protein is a type of transporter protein which enables two different molecules to cross the cell membrane at the same time. The two molecules however must be in contact with the symport in order for it to act.
Their transport occurs along the electrochemical gradient of the molecules in question on either side of the membrane.
Function of the symport protein
The symport proteins are partly responsible (along with the uniport proteins) for facilitated diffusion of solutes across the cell and organelle membranes.
The different types of facilitated diffusion transporter proteins. M is a section through the cell membrane. A symport protein is shown in II © Zoph, Wikimedia CC by-sa 3.0