Effects of Introducing Fibrinogen Aα Character into the Factor XIII Activation Peptide Segment

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• 作者：Madhavi A. Jadhav ; Giulia Isetti ; Toni A. Trumbo ; Muriel C. Maurer
• 刊名：Biochemistry
• 出版年：2010
• 出版时间：April 6, 2010
• 年：2010
• 卷：49
• 期：13
• 页码：2918-2924
• 全文大小：790K
• 年卷期：v.49,no.13(April 6, 2010)
• ISSN：1520-4995

文摘

The formation of a blood clot involves the interplay of thrombin, fibrinogen, and Factor XIII. Thrombin cleaves fibrinopeptides A and B from the N-termini of the fibrinogen Aα and Bβ chains. Fibrin monomers are generated that then polymerize into a noncovalently associated network. By hydrolyzing the Factor XIII activation peptide segment at the R37−G38 peptide bond, thrombin assists in activating the transglutaminase FXIIIa that incorporates cross-links into the fibrin clot. In this work, the kinetic effects of introducing fibrinogen Aα character into the FXIII AP segment were examined. Approximately 25% of fibrinogen Aα is phosphorylated at Ser3, producing a segment with improved binding to thrombin. FXIII AP (²²AEDDL²⁶) has sequence properties in common with Fbg Aα (¹ADSpGE⁵). Kinetic benefits to FXIII AP cleavage were explored by extending FXIII AP (28−41) to FXIII AP (22−41) and examining peptides with D24, D24S, D24Sp, and D24Sp P27G. These modifications did not provide the same kinetic advantages that were observed with Fbg Aα (1−20) S3p. Such results further emphasize that FXIII AP derives most of its substrate specificity from the P₉−P₁ segment. To enhance the kinetic properties of FXIII AP (28−41), we introduced substitutions at the P₉, P₄, and P₃ positions. Studies reveal that FXIII AP (28−41) V29F, V34G, V35G exhibits kinetic improvements that are comparable to those of FXIII AP V29F, V34L and approach those of Fbg Aα (7−20). Selective changes to the FXIII AP segment sequence may be used to design FXIII species that can be activated more or less readily.