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PDBsum entry 2dg2
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Protein binding
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PDB id
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2dg2
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References listed in PDB file
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Key reference
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Title
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Biochemical and structural characterization of apolipoprotein a-I binding protein, A novel phosphoprotein with a potential role in sperm capacitation.
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Authors
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K.N.Jha,
I.A.Shumilin,
L.C.Digilio,
O.Chertihin,
H.Zheng,
G.Schmitz,
P.E.Visconti,
C.J.Flickinger,
W.Minor,
J.C.Herr.
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Ref.
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Endocrinology, 2008,
149,
2108-2120.
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PubMed id
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Abstract
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The physiological changes that sperm undergo in the female reproductive tract
rendering them fertilization-competent constitute the phenomenon of
capacitation. Cholesterol efflux from the sperm surface and protein kinase A
(PKA)-dependent phosphorylation play major regulatory roles in capacitation, but
the link between these two phenomena is unknown. We report that apolipoprotein
A-I binding protein (AI-BP) is phosphorylated downstream to PKA activation,
localizes to both sperm head and tail domains, and is released from the sperm
into the media during in vitro capacitation. AI-BP interacts with apolipoprotein
A-I, the component of high-density lipoprotein involved in cholesterol
transport. The crystal structure demonstrates that the subunit of the AI-BP
homodimer has a Rossmann-like fold. The protein surface has a large two
compartment cavity lined with conserved residues. This cavity is likely to
constitute an active site, suggesting that AI-BP functions as an enzyme. The
presence of AI-BP in sperm, its phosphorylation by PKA, and its release during
capacitation suggest that AI-BP plays an important role in capacitation possibly
providing a link between protein phosphorylation and cholesterol efflux.
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