Calmodulin-binding proteins in granule and plasma membranes from bovine chromaffin cells

Block, Jan De; Petit, Koen; Laer, Lutgart Van; Dillen, Lieve; Roggen, Erwin L.; Potter, W.P. De

doi:10.1016/0005-2736(90)90248-m

Cited by 3 publications

(1 citation statement)

References 29 publications

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“…AIIt-Dependent Plasma Membrane-Chromaffin Granule Complex Formation. Plasma membrane was isolated and purified from bovine adrenal medulla as per the method of De Block et al (1990). Typically, 0.1 mg of chromaffin granules was incubated in the presence or absence of 1.23 /rM Allt and 0.21 mg of purified plasma membrane in a buffer containing 0.3 M sucrose, 25 mM HEPES (pH 7.5), 20 pM CaCl2, and 30 mM KC1 for 15 min at 20 °C.…”

Section: Methodsmentioning

confidence: 99%

Modulation of annexin II tetramer by tyrosine phosphorylation

Hubaishy¹,

Jones²,

Bjorge³

et al. 1995

Biochemistry

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Annexin II tetramer (AIIt) is a Ca(2+)-dependent phospholipid-binding phosphoprotein. In cells either expressing transforming protein tyrosine kinases or treated with growth factors such as PDGF, AIIt has been shown to contain increased levels of phosphotyrosine. Therefore, we have examined the effects of the in vitro phosphorylation of AIIt by pp60c-src on several activities of the protein. AIIt was phosphorylated by pp60c-src to 0.91 +/- 0.07 mol of phosphate/mol of AIIt (mean +/- SD). The protein tyrosine phosphorylation of AIIt completely inhibited the ability of the protein to bind to and bundle F-actin. In contrast, the phosphoprotein and native protein bound to purified adrenal medulla chromaffin granules with similar affinity; however, the chromaffin granule bridging activity of the phosphoprotein was abolished. The inhibition of the chromaffin granule bridging activity of the phosphoprotein could be partially reversed by the addition of millimolar Ca2+. Furthermore, the phosphorylation of AIIt by pp60c-src inhibited the in vitro ability of this annexin to form a complex consisting of plasma membrane, chromaffin granules, and AIIt. In addition to binding to biological membranes, some annexin proteins have been shown to possess carbohydrate-binding activity. Although native AIIt bound to a heparin affinity column, tyrosine phosphorylation of AIIt blocked the ability of the protein to bind to the heparin affinity column. These results suggest that the tyrosine phosphorylation of AIIt is a negative modulator of AIIt and that the dephosphorylation of AIIt might be necessary for activation of the protein.

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Section: Methodsmentioning

confidence: 99%