Calcium-binding protein of chorioallantoic membrane: identification and development expression.

Abstract

A calcium-binding protein (CaBP) which has a molecular weight of 100,000 and an isoelectric point of 8.0 has been isolated from the chorioallantoic membrane (CAM) of the chick embryo. Expression of the CaBP occurs simultaneously with the onset of calcium absorption from the egg shell by the CAM, and the temporal increase in CaBP activity is coincident with calcium deposition in the embryo. The CAM CaBP differs in properties from the CaBPs of the adult organs, including the vitamin-D-dependent protein of intestine.

Functional involvement of carbonic anhydrase in calcium transport of the chick chorioallantoic membrane

“…One of the mechanisms appears to be the expression of a specific Ca2+-binding protein (Tuan & Scott, 1977;Tuan et al, 1978a). In this report we have presented evidence strongly indicating that the expression of carbonic anhydrase activity is also important in the Ca2+-transport function of the chorioallantoic membrane.…”

“…5. Effects of sulphanilamide on the Ca2+-binding activity of chorioallantoic-membrane extract from 19-day embryos The chorioallantoic-membrane extract was prepared and Ca2+-binding activities were determined as described previously (Tuan & Scott, 1977;Tuan et al, 1978a Vol. 176 in the extracts prepared from the segment of chorioallantoic membrane directly forming the uptake chamber is specifically inhibited.…”

“…The chorioallantoic membrane was dissected out from the embryos and extracts of the membrane were prepared as previously described (Tuan & Scott, 1977) in 0.02M-Tris/HCl buffer, pH 8.0.…”

“…Ca2+-binding activity was assayed by the Chelex 100 ion-exchange method (Tuan & Scott, 1977). Determination of haemoglobin was carried out by the cyanomethaemoglobin method (Cannan, 1958) (1976) with 45CaC12 (New England Nuclear, Boston, MA, U.S.A.; 1-2pCi/#mol of 40Ca) as at racer in the uptake buffer (1.2mM-MgSO4, 25.0mM-NaHCO3, 0.11 M-NaCl, 6.0mM-KCl, 1 .0 mM-Na2HPO4, 4.4 mMglucose, 1.OmM-CaCl2, pH7.4).…”

“…The exact mechanism of Ca2+ transport by the chorioallantoic membrane is not yet understood. However, we have identified and isolated from the chorioallantoic membrane a Ca2+-binding protein that appears to be functionally involved in the Ca2+-transport process (Tuan & Scott, 1977;Tuan et al, 1978a).…”