Studies on prolactin: conformational comparison of human, equine, and porcine pituitary prolactins.

The research compares the structure and properties of the hormone prolactin in humans, horses, and pigs, revealing their high similarity across these species. Prolactin concentration measures are provided, aiding accuracy in biological and medical research.

Research Overview

• The study focuses on comparing the conformations or structures of the hormone prolactin in humans, horses, and pigs.
• The researchers utilized several optical properties like direct absorption, fluorescence emission, and circular dichroism spectra to gather evidence of the similarities and differences in these hormones.

Similarities in Prolactin Across Species

• The research found that the alpha-helix content, a specific structural element in proteins, of prolactins in all three species was roughly the same (60 ± 5%).
• The side chains of two of the amino acids that make up these proteins, tyrosine and tryptophan, were found to exist in similar microenvironments within the folded forms of the hormones in these species.
• These findings suggest that the general conformations or structures of prolactins in different species are closely related to each other.

Measuring Prolactin Concentration

• Molar extinction and absorptivity values were obtained at the absorption maximum of each species, which helped in determining accurate prolactin concentrations ranging from 10(0) to 10(-2) mg/ml.
• A second molar extinction value was determined at a unique wavelength for each species, independent of the conformational state of the molecule.

Prolactin Reaction to Proteolytic Enzyme Thermolysin

• When the three types of prolactin hormones were incubated with the protease thermolysin, the proteins underwent an initial short lag period during which little change in their conformation could be observed.
• However, the speed at which the proteins then collapsed, under the action of thermolysin, varied across species. While the prolactin from humans and pigs displayed similar rates of collapse, the horse prolactin’s structure decayed more slowly under the same conditions.