Related topics: protein

Fitting a right hand in a left-handed mitten

Many biomolecules come in two versions that are each other's mirror image, like a left and a right hand. Cells generally use the left-hand version of amino acids to produce proteins, and uptake mechanisms were thought to ...

Multiple modes for selectivity of transmembrane transport

LMU researchers utilized a biophysical approach to understand how bacterial import proteins bind and selectively convey their cargoes across membranes. The results reveal an unexpectedly wide variety of transfer mechanisms.

New insight into unique sugar transport in plants

Sugar transport through sugar transport proteins (STP) is unique to plants, and is important for the proper development of plant organs such as pollen. STPs are also used to concentrate sugars in specific tissues like fruit, ...

How plants bind their green pigment chlorophyll

Chlorophyll is the pigment used by all plants for photosynthesis. There are two versions, chlorophyll a and chlorophyll b. These are structurally very similar to one another but have different colors, blue-green and yellowish ...

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Carrier protein

Carrier proteins are proteins that transport a specific substance or group of substances through intracellular compartments or in extracellular fluids (e.g. in the blood) or else across the cell membrane. Some of the carriers are water-soluble proteins that may or may not interact with biological membranes, such as some transporters of small hydrophobic molecules, whereas others are integral transmembrane proteins.

Carrier proteins transport substances out of or into the cell by facilitated diffusion and active transport. Each carrier protein is designed to recognize only one substance or one group of very similar substances. The molecule or ion to be transported (the substrate) must first bind at a binding site at the carrier molecule, with a certain binding affinity. Following binding, and while the binding site is facing, say, outwards, the carrier will capture or occlude (take in and retain) the substrate within its molecular structure and cause an internal translocation, so that it now faces the other side of the membrane. The substrate is finally released at that site, according to its binding affinity there. All steps are reversible.

For example:

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