Sialic acid-binding Ig-like lectin 12, or Siglec-XII, is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

that in humans, is encoded by the ''SIGLEC12''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

Sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this ...

-binding immunoglobulin-like

lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in rec ...

s ( SIGLECs) are a family of cell surface

s belonging to the

immunoglobulin superfamily The immunoglobulin superfamily (IgSF) is a large protein superfamily of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily ...

. They mediate protein-carbohydrate interactions by selectively binding to different

sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this ...

moieties present on

glycolipid Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the conne ...

s and

glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as g ...

s. This gene encodes a member of the SIGLEC3-like subfamily of SIGLECs. Members of this subfamily are characterized by an extracellular V-set immunoglobulin-like domain followed by two C2-set immunoglobulin-like domains, and the cytoplasmic tyrosine-based motifs, ITIM and SLAM-like. The encoded protein, upon tyrosine phosphorylation, has been shown to recruit the Src homology 2 domain-containing protein-tyrosine phosphatases SHP1 and SHP2. It has been suggested that the protein is involved in the negative regulation of macrophage signaling by functioning as an inhibitory receptor. This gene is located in a cluster with other SIGLEC3-like genes on 19q13.4. Alternatively spliced transcript variants encoding distinct isoforms have been described for this gene. The Siglec-XII protein has been identified as a possible promoter of human carcinoma progression in research by Ajit Varki and Nissi Varki at the University of California San Diego School of Medicine. Approximately seventy percent of humans have a mutation that inactivates the protein, but those without the mutation may suffer an inordinate number of carcinomas when compared to other primates. Jones, Asher,
“Rogue” Protein Could Contribute to Humans’ High Cancer Rates
', The Scientist, April 1, 2021 The research is being conducted to determine whether inactivation of the gene might deter its promotional effect upon the progression of human carcinoma.

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