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Lipovitellin 2β is the 31 kD Ni 2+ ‐binding protein ( pNiXb ) in Xenopus oocytes and embryos
Author(s) -
GrbacIvankovic Svetlana,
Antonijczuk Katarzyna,
Varghese Alison H.,
Plowman Marilyn C.,
Antonijczuk Adam,
Korza George,
Ozols Juris,
Sunderman F. William
Publication year - 1994
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.1080380305
Subject(s) - xenopus , biology , vitellogenin , microbiology and biotechnology , yolk , ammonium sulfate precipitation , embryo , size exclusion chromatography , biochemistry , gene , enzyme , ecology
An Ni 2+ ‐binding protein ( pNiXb , 31 kD) present in mature Xenopus laevis oocytes and in embryos from fertilization in N/F stage 42, was isolated and characterized. After oocytes or embryos were fractionated by PAGE, electroblotted onto nitrocellulose, and probed with 63 Ni 2+ , pNiXb was detected by autoradiography. pNiXb , a yolk protein located in the embryonic gut, was purified from yolk platelets by ammonium sulfate precipitation, delipidation, gel filtration chromatography, and HPLC analysis. During these steps, pNiXb copurified with lipovitellin 2. The N‐terminal sequence of purified pNiXb exactly matched that of Xenopus lipovitellin 2β, deduced from the DNA sequence of the Xenopus vitellogenin A2 precursor gene. Since pNiXb and lipovitellin 2β agree in N‐terminal sequence, amino acid composition, and apparent molecular weight, they appear to be identical. Based on a metalblot competition assay, the abilities of metal ions to compete with 63 Ni 2+ for binding to pNiXb were ranked: Zn 2+ ≈ Cu 2+ ≈ Co 2+ > Cd 2+ ≈ Mn 2+ > Sn 2+ . This study shows that Xenopus lipovitellin 2β is a metal‐binding protein in vitro, and raises the possibility that it may function similarly in vivo. © 1994 Wiley‐Liss, Inc.