Glycosylation at Asn-289 facilitates the ligand-induced conformational changes of human Glu-plasminogen.
Glu-plasminogen exists in two major glycoforms (I and II). Glycoform I contains carbohydrate chains linked to Asn-289 and Thr-346, whereas glycoform II is glycosylated only at Thr-346. Disparities in carbohydrate content lead to differences in the important functional properties of the zymogen, e.g. the kinetics of activation. The kinetics of the large ligand-induced conformational changes of each of the Glu-plasminogen glycoforms have been studied using stopped-flow fluorescence. The results are in accordance with a conformational change governed by positive co-operative binding at two weak lysine-binding sites. Additional glycosylation at Asn-289 in Glu-plasminogen I results in a two-fold increase in the overall dissociation constant of a ligand, trans-4-aminomethyl-cyclohexane carboxylic acid. This effect stems directly from the reaction step during which the conformational changes occur. This implies a higher population of Glu-plasminogen I in the open conformation even in the absence of ligands, and thus accounts for a higher rate of activation of Glu-plasminogen I, in comparison with Glu-plasminogen II.
Mølgaard
L
L
Biologics Development, Novo Nordisk A/S, Gentofte, Denmark.
Ponting
C P
CP
Christensen
U
U
D001216:Asparagine; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D006031:Glycosylation; D006801:Humans; D007700:Kinetics; D008024:Ligands; D010958:Plasminogen / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D014148:Tranexamic Acid / Q000737:chemistry
D006023:Glycoproteins; D008024:Ligands; D014148:Tranexamic Acid; D001216:Asparagine; D010958:Plasminogen