{"entryType":"UniProtKB reviewed (Swiss-Prot)","primaryAccession":"Q925E8","uniProtkbId":"SPTSB_MOUSE","entryAudit":{"firstPublicDate":"2006-06-13","lastAnnotationUpdateDate":"2026-09-02","lastSequenceUpdateDate":"2001-12-01","entryVersion":127,"sequenceVersion":1},"annotationScore":4.0,"organism":{"scientificName":"Mus musculus","commonName":"Mouse","taxonId":10090,"lineage":["Eukaryota","Metazoa","Chordata","Craniata","Vertebrata","Euteleostomi","Mammalia","Eutheria","Euarchontoglires","Glires","Rodentia","Myomorpha","Muroidea","Muridae","Murinae","Mus","Mus"]},"proteinExistence":"1: Evidence at protein level","proteinDescription":{"recommendedName":{"fullName":{"value":"Serine palmitoyltransferase small subunit B"}},"alternativeNames":[{"fullName":{"value":"Protein ADMP"}},{"fullName":{"value":"Small subunit of serine palmitoyltransferase B"},"shortNames":[{"value":"ssSPTb"}]}]},"genes":[{"geneName":{"value":"Sptssb"},"synonyms":[{"value":"Admp"},{"value":"Sssptb"}]}],"comments":[{"texts":[{"evidences":[{"evidenceCode":"ECO:0000250","source":"UniProtKB","id":"Q8NFR3"}],"value":"Component of the serine palmitoyltransferase multisubunit enzyme (SPT) that catalyzes the initial and rate-limiting step in sphingolipid biosynthesis by condensing L-serine and activated acyl-CoA (most commonly palmitoyl-CoA) to form long-chain bases. The SPT complex is composed of SPTLC1, SPTLC2 or SPTLC3 and SPTSSA or SPTSSB. Within this complex, the heterodimer consisting of SPTLC1 and SPTLC2/SPTLC3 forms the catalytic core. Within the SPT complex, SPTSSB stimulates the catalytic activity and plays a role in substrate specificity. SPT complexes with this subunit showing a preference for longer acyl-CoAs. The SPTLC1-SPTLC2-SPTSSB complex shows a strong preference for C18-CoA substrate, while the SPTLC1-SPTLC3-SPTSSB isozyme displays an ability to use a broader range of acyl-CoAs, without apparent preference"}],"commentType":"FUNCTION"},{"texts":[{"evidences":[{"evidenceCode":"ECO:0000269","source":"PubMed","id":"26438849"}],"value":"Lipid metabolism; sphingolipid metabolism"}],"commentType":"PATHWAY"},{"texts":[{"evidences":[{"evidenceCode":"ECO:0000250","source":"UniProtKB","id":"Q8NFR3"},{"evidenceCode":"ECO:0000250","source":"UniProtKB","id":"Q969W0"}],"value":"Component of the serine palmitoyltransferase (SPT) complex, which is composed of SPTLC1, SPTLC2 or SPTLC3 and SPTSSA or SPTSSB. The heterodimer consisting of SPTLC1 and SPTLC2/SPTLC3 forms the catalytic core of the enzyme, while SPTSSA or SPTSSB subunits determine substrate specificity (By similarity). SPT also interacts with ORMDL proteins, especially ORMDL3, which negatively regulate SPT activity in the presence of ceramides (By similarity)"}],"commentType":"SUBUNIT"},{"commentType":"SUBCELLULAR LOCATION","subcellularLocations":[{"location":{"evidences":[{"evidenceCode":"ECO:0000305"}],"value":"Endoplasmic reticulum membrane","id":"SL-0097"},"topology":{"evidences":[{"evidenceCode":"ECO:0000305"}],"value":"Multi-pass membrane protein","id":"SL-9909"}}]},{"texts":[{"evidences":[{"evidenceCode":"ECO:0000269","source":"PubMed","id":"15777716"}],"value":"Expression is strong in hypogonadal (hpg) mouse prostate, weak in mature castrated mouse prostate and absent in normal intact or androgen-replaced hpg mouse prostates"}],"commentType":"TISSUE SPECIFICITY"},{"texts":[{"evidences":[{"evidenceCode":"ECO:0000269","source":"PubMed","id":"15777716"}],"value":"While expression is androgen independent in the hpg mouse prostate, it appears to be androgen-dependent in the kidney and brain of normal intact mouse suggesting tissue specific regulation by androgens"}],"commentType":"INDUCTION"},{"texts":[{"evidences":[{"evidenceCode":"ECO:0000305"}],"value":"Belongs to the SPTSS family. SPTSSB subfamily"}],"commentType":"SIMILARITY"}],"features":[{"type":"Chain","location":{"start":{"value":1,"modifier":"EXACT"},"end":{"value":76,"modifier":"EXACT"}},"description":"Serine palmitoyltransferase small subunit B","featureId":"PRO_0000239720"},{"type":"Topological domain","location":{"start":{"value":1,"modifier":"EXACT"},"end":{"value":11,"modifier":"EXACT"}},"description":"Cytoplasmic","evidences":[{"evidenceCode":"ECO:0000255"}]},{"type":"Transmembrane","location":{"start":{"value":12,"modifier":"EXACT"},"end":{"value":29,"modifier":"EXACT"}},"description":"Helical","evidences":[{"evidenceCode":"ECO:0000255"}]},{"type":"Topological domain","location":{"start":{"value":30,"modifier":"EXACT"},"end":{"value":36,"modifier":"EXACT"}},"description":"Lumenal","evidences":[{"evidenceCode":"ECO:0000255"}]},{"type":"Transmembrane","location":{"start":{"value":37,"modifier":"EXACT"},"end":{"value":57,"modifier":"EXACT"}},"description":"Helical","evidences":[{"evidenceCode":"ECO:0000255"}]},{"type":"Topological domain","location":{"start":{"value":58,"modifier":"EXACT"},"end":{"value":76,"modifier":"EXACT"}},"description":"Cytoplasmic","evidences":[{"evidenceCode":"ECO:0000255"}]},{"type":"Mutagenesis","location":{"start":{"value":56,"modifier":"EXACT"},"end":{"value":56,"modifier":"EXACT"}},"description":"Mutant mice develop early onset ataxia, exhibit reduced body weight and usually die around 10 weeks after birth. Increases SPT affininity toward C18-CoA substrate by twofold and elevates C20 long chain base production in the brain and eye. Produces neurodegenerative effects such as aberrant membrane structures, accumulation of ubiquitinated protein on membranes and axon degeneration.","evidences":[{"evidenceCode":"ECO:0000269","source":"PubMed","id":"26438849"}],"alternativeSequence":{"originalSequence":"H","alternativeSequences":["L"]}}],"keywords":[{"id":"KW-0256","category":"Cellular component","name":"Endoplasmic reticulum"},{"id":"KW-0443","category":"Biological process","name":"Lipid metabolism"},{"id":"KW-0472","category":"Cellular component","name":"Membrane"},{"id":"KW-1185","category":"Technical term","name":"Reference proteome"},{"id":"KW-0746","category":"Biological process","name":"Sphingolipid metabolism"},{"id":"KW-0812","category":"Domain","name":"Transmembrane"},{"id":"KW-1133","category":"Domain","name":"Transmembrane helix"}],"references":[{"referenceNumber":1,"citation":{"id":"15777716","citationType":"journal article","authors":["Singh J.","Young L.","Handelsman D.J.","Dong 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