Characterization of the post‐translational modification of recombinant human BMP‐15 mature protein

Abstract

Bone morphogenetic protein‐15 (BMP‐15) is an oocyte‐secreted factor critical for the regulation of ovarian physiology. When recombinant human BMP‐15 (rhBMP‐15) produced in human embryonic kidney 293 cells was subjected to SDS‐PAGE analysis, two mature protein forms corresponding to 16 kDa (P16) and 17 kDa (P17) were observed. Despite the physiological relevance and critical function of BMP‐15 in female reproduction, little is known about the structure of rhBMP‐15. Here, we have analyzed the structure of the rhBMP‐15 mature proteins (P16 and P17) using state‐of‐the‐art proteomics technology. Our findings are as follows: (1) the N‐terminal amino acid of P16 and P17 is pyroglutamic acid; (2) the Ser residue at the sixth position of P16 is phosphorylated; (3) P17 is O‐glycosylated at Thr¹⁰; and (4) the C‐terminal amino acid of P16 and P17 is truncated. These findings are the first knowledge of the structure of rhBMP‐15 mature protein toward understanding the molecular basis of BMP‐15 function and could provide an important contribution to the rapidly progressing research area involving oocyte‐specific growth factors in modulation of female fertility.