Stabilization of bovine trypsin by reductive methylation

Reductive methylation has little or no detectable effect on the catalytic or physicochemical properties of bovine trypsin but reduces its susceptibility to autolysis. Increased stability after methylation appears to result from the conversion of trypsin-susceptible lysine residues to trypsin-resistant epsilon-N,N-dimethyllysine residues. Reductively methylated trypsin is easily prepared and may be useful in place of trypsin where autolysis is otherwise difficult to control.

The cornified envelope of terminally differentiated human epidermal keratinocytes consists of cross-linked protein

A small proportion of the protein of stratum corneum of human epidermal callus is insoluble even when boiled in solutions containing sodium dodecylsulfate and a reducing agent. This protein is present in the cornified envelope, a structure located beneath the plasma membrane. When cornified envelopes were dissolved by exhaustive proteolytic digestion and the products analyzed by chromatography, approximately 18% of the total lysine residues were found as the cross-linking dipeptide epsilon-(gamma-glutamyl) lysine. Labeled cornified envelope protein was synthesized by human epidermal keratinocytes allowed to differentiate terminally in culture. The extent of cross-linking, determined from the proportion of radioactive lysine in epsilon-(gamma-glutamyl) lysine after exhaustive proteolysis, was similar to that in stratum corneum. The properties of the cornified envelopes (insolubility in detergent and reducing agents, and solubility following proteolytic digestion) are readily explained by a structure consisting of a cross-linked protein lattice.

Wheat germ agglutinin. Evidence for a genetic basis of multiple forms

Germ from hexaploid wheat (Triticum aestivum L.) contained three forms of agglutinin separable by ion-exchange column chromatography at pH 3.8, while germ from tetraploid wheat (Triticum turgidum L. (durum group)) contained only two such forms. The different number of forms, not due to protein modification occurring during the purification process, was demonstrable in commercial germ and in bran fractions containing germ from single wheat varieties. This evidence for a genetic basis of lectin multiple forms in wheat indicates the advisability of using genetically identified plant varieties in lectin research.