Atypical Solute Carrier Families (Atypical SLCs) are novel plausible secondary active or facilitative transporter proteins that share ancestral background with the known solute carrier families (SLCs). However, they have not been assigned a name according to the SLC root system, or been classified into any of the existing SLC families.

Atypical major facilitator superfamily transport families

Most atypical SLCs are

families Family (from ) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictability, structure, and safety as ...

within the

major facilitator superfamily The major facilitator superfamily (MFS) is a Protein superfamily, superfamily of membrane transport proteins that facilitate movement of small solutes across cell membranes in response to chemiosmosis, chemiosmotic gradients. Function The major ...

(MFS). These atypical SLCs are plausible secondary active or facilitative transporter proteins that share ancestry with the known solute carriers. They are, however, not named according to the SLC root system, or classified into any of the existing SLC families. Atypical MFS transporter families (ATMFs) are categorised based on their sequence similarity and phylogenetic closeness. Some Atypical SLC of MFS type are:

OCA2 P protein, also known as melanocyte-specific transporter protein or pink-eyed dilution protein homolog, is a protein that in humans is encoded by the oculocutaneous albinism II (''OCA2'') gene. The P protein is believed to be an integral membrane ...

CLN3 Battenin is a protein that in humans is encoded by the ''CLN3'' gene located on chromosome 16. Battenin is not clustered into any Pfam clan, but it is included in the TCDB suggesting that it is a transporter. In humans, it belongs to the atypi ...

, SPNS1, SPNS2, SPNS3,

SV2A Synaptic vesicle glycoprotein 2A (SV2A) is a transmembrane protein belonging to a family of keratan sulfate Proteoglycan, proteoglycans, located on the synaptic vesicle, synaptic vesicles of mammalian neuronal and endocrine cells. It's encoded by ...

SV2B Synaptic vesicle glycoprotein 2B is a protein that in humans is encoded by the ''SV2B'' gene. See also * SV2A Synaptic vesicle glycoprotein 2A (SV2A) is a transmembrane protein belonging to a family of keratan sulfate Proteoglycan, proteoglycan ...

, SV2C, SVOP, SVOPL,

MFSD1 Major facilitator superfamily domain containing 1 (MFSD1, SMAP) is a protein belonging to the MFS Pfam clan. It is an Atypical solute carrier. It belongs to the major facilitator superfamily MFS Pfam Pfam is a database of protein families th ...

, MFSD2A, MFSD2B,

MFSD3 Major facilitator superfamily domain containing 3 (MFSD3) is a protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of f ...

, MFSD4A, MFSD4B, MFSD5, MFSD6, MFSD6L,

MFSD8 Major facilitator superfamily domain containing 8 also called MFSD8 is a protein that in humans is encoded by the ''MFSD8'' gene. MFSD8 is an atypical SLC, thus a predicted SLC transporter. It clusters phylogenetically to the Atypical MFS Trans ...

MFSD9 Major facilitator superfamily domain-containing protein 9 is a protein that in humans is encoded by the MFSD9 gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence ...

, MFSD10,

MFSD11 Major facilitator superfamily The major facilitator superfamily (MFS) is a Protein superfamily, superfamily of membrane transport proteins that facilitate movement of small solutes across cell membranes in response to chemiosmosis, chemiosmotic gr ...

, MFSD12, MFSD13A, MFSD14A,

MFSD14B Major facilitator superfamily The major facilitator superfamily (MFS) is a Protein superfamily, superfamily of membrane transport proteins that facilitate movement of small solutes across cell membranes in response to chemiosmosis, chemiosmotic gr ...

UNC93A Unc-93 homolog A (C. elegans) is a protein that in humans is encoded by the UNC93A gene. Unc93A is a major facilitator superfamily (MFS), and a putative solute carrier in humans. It belongs to the atypical SLCs that was recently listed. It is t ...

and

UNC93B1 Unc-93 homolog B1 ('' C. elegans''), also known as UNC93B1, is a protein which in humans is encoded by the ''UNC93B1'' gene. Function This gene encodes a protein with similarity to the ''Caenorhabditis elegans ''Caenorhabditis elegans'' ( ...

. All these are atypical SLCs found within the

Major facilitator superfamily The major facilitator superfamily (MFS) is a Protein superfamily, superfamily of membrane transport proteins that facilitate movement of small solutes across cell membranes in response to chemiosmosis, chemiosmotic gradients. Function The major ...

. Also TMEM104 (APC clan), OCA2 (IT clan) and CLN3 (having no clan) are atypical SLCs in humans.

Non-MFS transport families

Although most atypical SLCs are from the major facilitator superfamily, there are exceptions: TMEM104 ( APC superfamily), OCA2 (IT superfamily) and CLN3 (unknown superfamily).

References

Solute carrier family {{genetics-stub