1B2T, 1F2L, 3ONA, 4XT1, 4XT3637620312ENSG00000006210ENSMUSG00000031778P78423O35188NM_002996NM_001304392NM_009142NP_001291321NP_002987NP_033168Fractalkine, also known as chemokine (C-X3-C motif) ligand 1, is a protein that in humans is encoded by the CX3CL1 gene.

Fractalkine is a large cytokine protein of 373 amino acids that contains multiple domains and is the only known member of the CX3C chemokine family.

For example, the spacing of the characteristic N-terminal cysteines differs; there are three amino acids separating the initial pair of cysteines in CX3CL1, with none in CC chemokines and only one intervening amino acid in CXC chemokines.

CX3CL1 is produced as a long protein (with 373-amino acid in humans) with an extended mucin-like stalk and a chemokine domain on top.

[9] CX3CL1 is also up-regulated in the hippocampus during a brief temporal window following spatial learning, the purpose of which may be to regulate glutamate-mediated neurotransmission tone.