Characterization of the murine corticosteroid binding globulin: variations between mammalian forms

Area of Science:

• Biochemistry
• Proteomics
• Comparative genomics

Background:

• Corticosteroid-binding globulin (CBG) is a key plasma protein involved in steroid hormone transport.
• Understanding species-specific variations in CBG is crucial for interpreting steroid signaling and drug metabolism.
• Previous studies provided an indirectly deduced human CBG amino acid sequence.

Purpose of the Study:

• To isolate and characterize corticosteroid-binding globulin (CBG) from term-pregnant mouse serum.
• To compare the amino acid sequence of mouse CBG with the previously reported human sequence.
• To investigate potential differences in glycosylation sites and immunological properties.

Main Methods:

• Isolation of CBG from term-pregnant mouse serum.
• Peptide analysis using CNBr and Lys-specific protease.
• Amino acid sequence analysis of six protein segments.
• Electrophoresis and immunological characterization of CBG variants.

Main Results:

• Six segments of mouse CBG, totaling 189 positions, were sequenced.
• Overall homology between mouse and human CBG sequences was unexpectedly low at 60%.
• Specific segments showed higher similarity to human counterparts.
• Differences were identified in at least two of six potential N-linked glycosylation sites.
• Electrophoretic variants and immunological properties of mouse CBG were described.

Conclusions:

• Mouse CBG exhibits significant sequence divergence from human CBG, particularly in glycosylation sites.
• These structural differences may influence CBG's binding affinity, stability, and physiological roles in mice compared to humans.
• Further research is needed to fully elucidate the functional implications of these species-specific CBG variations.