alpha-2-HS-glycoprotein; alpha-2-Z-globulin; Ba-alpha-2-glycoprotein; fetuin-A (AHSG, FETUA, PRO2743)

Function

• negative acute phase reactant
• promotes endocytosis
• has opsonic properties
• influences the mineral phase of bone
• affinity for Ca+2 & Ba+2
• phosphorylation sites are present in the extracellular medium
• alpha-2-HS glycoprotein derived from cleavage of connecting peptide from precursor
• two chains A & B are held together by a single disulfide bond

Structure

• O-glycosylated & N-glycosylated
  • O-glycosylated with core 1 glycan or possibly core 8 glycan
    • N-glycan at Asn-156: hex5hexNAc4; N-glycan
    • heterogeneity at Asn-176: hex5hexNAc4 (major) & hex6hexNAc5 (minor)
• belongs to the fetuin family
• contains 2 cystatin fetuin-A-type domains

Compartment

• secreted
• concentrated up to 300-fold in bone relative to other plasma proteins

Expression

• synthesized in liver
• secreted in plasma
• selectively concentrated in bone matrix
• also found in dentin in much higher quantities than other plasma proteins

Polymorphism

• two common alleles, AHSG*1 & AHSG*2
• AHSG*1 has Thr-248/Thr-256; AHSG*2 has Met-248/Ser-256

More general terms

• alpha 2 globulin
• Ca+2 binding protein
• opsonin
• glycoprotein
• phosphoprotein
• multisubunit protein
• acute phase protein

Additional terms

• fetuin-B (Gugu, IRL685, 16G2, FETUB)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=197
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:197
• OMIM: https://mirror.omim.org/entry/138680
• UniProt: http://www.uniprot.org/uniprot/P02765.html