Glycoprotein Hormone Beta 5 (GPHb5)

GPHB5 is a cystine knot-forming polypeptide and a subunit of the dimeric glycoprotein hormone family .The deduced 130-amino acid precursor protein contains a 24-amino acid signal peptide at its N terminus, and the mature protein has a putative N-glycosylation site. GPB5 has 10 of the 12 cysteines conserved in classical beta subunits. Consequently, GPB5 has the 3 disulfide bridges within the cystine knot structure, but it lacks 1 of the 3 additional bridges found in classical beta subunits. Due to the truncated C terminus and absence of the third disulfide bridge, GPB5 lacks the seatbelt structure found in other beta subunits. However, it contains 2 putative hairpin loop regions below the cystine knot and a long loop above. PCR analysis of several human tissues detected GPB5 predominantly in brain and pituitary.