Egg white lysozyme is the major protein of the hen's egg vitelline membrane

Lysozyme accounts for 37% of the proteins of the hen's egg vitelline membrane. It can be extracted by salt solutions and purified by gel filtration on Sephadex G-50. There are no differences between the chemical and enzymic properties of egg white and vitelline membrane lysozymes. Vitelline membranes of ovarian eggs do not contain lysozyme. It is thus concluded that lysozyme is localized in the outer layer. Vitelline membranes from fertilized and unfertilized eggs contain the same amount of lysozyme; its percentage decreases after two days of incubation.     

Mode of interaction between lysozyme and the other proteins of the hen's egg vitelline membrane

Salt solutions and charged detergents are efficient solubilizing agents for ovovitelline membrane lysozyme. Reassociation experiments with chemically modified lysozymes indicate that positively charged amino acid residues of lysozyme (the epsilon-amino group of lysine and the guanidino group of arginine) are involved in the interaction with other proteins of the vitelline membrane. Exogenous proteins are adsorbed to lysozyme-free vitelline membranes, only if they have a high pI, comparable to that of lysozyme. It is concluded that the lysozyme-ovovitelline membrane interaction is predominantly ionic. An ovomucin-lysozyme complex is postulated as the major component of the outer layer of the membrane.     

Proteomic analysis of the chicken egg vitelline membrane

The avian vitelline membrane (VM) is a multilayered proteinaceous structure separating egg white from yolk. The innermost layer of the VM, deposited onto the oocyte plasma membrane in the ovary, corresponds to the mammalian zona pellucida (ZP). The outer layer is produced in the infundibulum, the first section of the oviduct. Using high-throughput, high-end LC-MS(n) 137 proteins were identified, only 13 of which were known previously to be components of the VM. Depending on the washing protocol, two largely overlapping, but not identical, sets of identified proteins were produced from water-washed and salt-washed VMs. Most of the components of the VM were known previously from other egg compartments, such as, for instance, the egg white proteins lysozyme C, ovalbumin, ovotransferrin, and ovomucin. Specific components of the VM not identified previously in other egg compartments included eight ZP proteins, oviductin protease, and two ATPases. The vitelline outer membrane protein (VMO) VMO II was identified as beta-defensin-11. The list of VM proteins presented in this report is by far the most comprehensive dataset available at present and complements proteomic analyses of chicken egg compartments published previously.     

Macromolecular components of the vitelline membrane of hen's egg. I. Membrane structure and its deterioration with age.

The vitelline membrane of hen's egg has been successfully solubilized in sodium dodecyl sulfate (SDS), guanidine hydrochloride and urea solutions, and its macromolecular components examined. SDS-gel electrophoresis of the membrane solution revealed the presence of three major components designated I, II, and III, all containing carbohydrate and protein. The approximate molecular weights of components I and II were 32,000 and 260,000, respectively, and the sedimentation coefficients were 2.2S and 4.3S. Component III was in an aggregated form which disintegrated into smaller components upon reduction with 2-mercaptoethanol. It was found that component II (4.3S component) deteriorated during storage of the egg with the concomitant formation of degraded components. The loss of this component was accompanied by a gradual decrease of the neutral sugar content of the vitelline membrane. On the basis of these data, the membrane structure and its deterioration during storage are discussed.     

Nucleoside triphosphatase from the hen's egg white and vitelline membrane: purification, properties and relation to similar enzymes from the oviduct.

Hen's egg white and vitelline membrane nucleoside triphosphatases were purified resulting in active soluble subunits with MR 260,000 +/- 10,000. PH optima are divalent cation dependent and situated at pH 6.2 and 8.0 with ATP and at pH 6.15 with ADP as substrate. Ca2+ and Mg2+ are activators. Km and Ki values for Pi and PPi were determined. The enzymes are specific neither for ATP nor for ADP alone. No separation between nucleoside triphosphatase and nucleoside diphosphatase could be achieved. Differences found in their action can be due to differences in organization and properties of the (intermediary) enzyme-substrate complexes. A close relationship exists with homologous enzymes found in oviductal secretory cells and in oviductal secretions.