Genetic Polymorphism of PAS-I, the Mucin-Like Glycoprotein of Bovine Milk Fat Globule Membrane

A sensitive analytical method based on gel electrophoresis and silver staining was developed to detect PAS-I, a glycoprotein of bovine milk fat globule membrane. Application of the method to samples of milk from individual animals demonstrated that PAS-I is polymorphic and established that it also occurs in the skim milk phase. This polymorphism consisted of two bands showing variable mobility among samples of individual animals. Band patterns for an individual persisted from one lactation to the next. Comparison of 12 dam-daughter pairs for PAS-I patterns indicated that each pair had at least one band matching in mobility. Milk from identical twins had identical PAS-I patterns. Two out of three sets of fraternal twins had one band that did not match. Based on these data and genetics established for a similar protein of human milk, two codominant alleles, one from the sire and the other from the dam, account for the two bands of PAS-I. The PAS-I band patterns may be related to inheritance of milk production and composition factors.