Recombinant Human Kininogen-1 Protein: Research Guide

Recombinant Human Kininogen-1 Protein is a critical multifunctional plasma glycoprotein that serves as the precursor of bradykinin and high-molecular-weight kinin, playing essential roles in the contact activation coagulation pathway, inflammatory signaling, and blood pressure regulation.

Product Name

Recombinant Human Kininogen-1 Protein

SKU

rp368842

Gene Name

KNG1

Protein Origin

Human

Primary Biological Role

Bradykinin precursor; participates in contact activation coagulation pathway and inflammatory responses

Key Interaction Partners

Factor XII (Hageman factor), Plasma Kallikrein, Factor XI

Biological Background and Function

Kininogen-1 (KNG1), also known as high-molecular-weight kininogen (HMWK) or Williams-Fitzgerald-Flaujeac factor, is a multifunctional plasma glycoprotein encoded by the KNG1 gene in humans. It is produced predominantly in the liver and secreted into the bloodstream, where it circulates as a key component of the kinin-kallikrein system.

KNG1 exists in two major splice isoforms: high-molecular-weight kininogen (HMWK) and low-molecular-weight kininogen (LMWK). HMWK is the predominant plasma form and is central to the intrinsic (contact activation) coagulation pathway, serving as a non-enzymatic cofactor that assembles Factor XII (Hageman factor), prekallikrein, and Factor XI on negatively charged surfaces.

Upon activation by plasma kallikrein, KNG1 releases the vasoactive nonapeptide bradykinin, which mediates vasodilation, increased vascular permeability, pain signaling, and inflammatory responses via its cognate receptors B1R and B2R. KNG1 therefore acts as a molecular bridge between coagulation and inflammation. Additional reported functions include inhibition of cysteine proteases via its D2 domain, antithrombotic activity, and roles in angiogenesis and cell adhesion.

Reconstitution and Storage Protocol

Proper reconstitution and storage of Recombinant Human Kininogen-1 Protein (rp368842) are critical to maintaining protein activity and experimental reproducibility. Follow the guidelines below for optimal results.

Reconstitution: Briefly centrifuge the vial before opening to consolidate any lyophilized material at the bottom. Reconstitute the protein in sterile, deionized water or an appropriate physiological buffer (e.g., PBS, pH 7.4) to a concentration recommended on the product datasheet. Allow the protein to dissolve gently by pipetting; avoid vigorous vortexing, which may cause denaturation or aggregation. If the protein is supplied in liquid form, mix gently before use.

Working Aliquots: To minimize freeze-thaw cycles, prepare single-use working aliquots after reconstitution and store them at −20°C or −80°C as appropriate. Do not refreeze thawed aliquots.

Storage Conditions: Store the lyophilized protein at −20°C, protected from light and moisture. Once reconstituted, short-term storage (up to 1 week) may be carried out at 2–8°C. For long-term storage, aliquot and freeze at −80°C. Addition of a carrier protein such as 0.1% BSA may enhance stability during storage.

Note: Consult the product-specific Certificate of Analysis (CoA) and datasheet (absea#PP-11972) for lot-specific reconstitution volumes, concentrations, and stability data.

Experimental Applications

Recombinant Human Kininogen-1 Protein (rp368842) is suitable for a range of in vitro research applications related to the coagulation, kinin, and inflammatory systems. Representative applications include:

• Coagulation Assays: KNG1 can be used to reconstitute KNG1-deficient plasma to study the role of HMWK in the intrinsic coagulation pathway, including activated partial thromboplastin time (aPTT) assays and contact activation studies.
• Protein–Protein Interaction Studies: Recombinant KNG1 is suitable for studying binding interactions with Factor XII, prekallikrein, Factor XI, and other contact phase proteins using techniques such as ELISA, surface plasmon resonance (SPR), and co-immunoprecipitation.
• Bradykinin Release Assays: KNG1 can serve as a substrate for plasma kallikrein activity assays, enabling measurement of bradykinin generation kinetics in controlled biochemical settings.
• Cell-Based Assays: The protein can be used to study receptor-mediated cell signaling (B1R/B2R), cell adhesion, and endothelial cell responses relevant to inflammation and vascular biology.
• Enzyme Inhibition Studies: The cysteine protease inhibitory function of the D2 domain can be assessed using established fluorometric or chromogenic substrates.
• Western Blot and ELISA Standards: Recombinant KNG1 can serve as a positive control or standard curve component in immunoassays detecting endogenous kininogen.

Always optimize protein concentrations, buffer conditions, and assay formats empirically for your specific experimental system.

Quality, Purity, and Specifications

Recombinant Human Kininogen-1 Protein (rp368842) from Aladdin Scientific is manufactured using recombinant expression systems to ensure consistency and reproducibility across lots. Key quality attributes typically assessed for recombinant proteins of this class include:

• Purity: Assessed by SDS-PAGE and/or HPLC; high-purity preparations minimize background in sensitive biochemical assays.
• Biological Activity: Confirmed by functional assay appropriate to the protein, such as coagulation reconstitution or kallikrein-mediated cleavage assay.
• Endotoxin Level: Tested by Limulus Amebocyte Lysate (LAL) assay; low endotoxin is critical for cell-based assays and in vivo studies.
• Molecular Weight Confirmation: Verified by reducing and non-reducing SDS-PAGE, consistent with the expected molecular weight of KNG1 isoform expressed.
• Sterility: Preparations intended for cell culture use are tested for sterility or filtered through 0.2 μm membranes.

Refer to the Certificate of Analysis (CoA) provided with each lot (absea#PP-11972) for lot-specific specifications, purity values, and activity data. Contact Aladdin Scientific technical support for custom specifications or bulk supply enquiries.

Frequently asked questions

What is Recombinant Human Kininogen-1 Protein used for in research?

Recombinant Human Kininogen-1 Protein (rp368842) is primarily used to study the kinin-kallikrein system, intrinsic coagulation pathway, and inflammatory signaling. Applications include coagulation reconstitution assays, protein-protein interaction studies with contact phase factors, bradykinin release assays, and as a positive control in ELISA and Western blot.

How should Recombinant Human Kininogen-1 Protein be reconstituted and stored?

Briefly centrifuge the vial, then reconstitute in sterile water or PBS (pH 7.4) at the concentration specified on the datasheet. Prepare single-use aliquots to avoid repeated freeze-thaw cycles. Store lyophilized protein at −20°C and reconstituted aliquots at −80°C for long-term use. Refer to the product CoA (absea#PP-11972) for lot-specific guidance.

What expression system is used to produce rp368842, and does it affect glycosylation?

The specific expression system for rp368842 (e.g., mammalian, insect, or E. coli) should be confirmed in the product datasheet or CoA, as this directly impacts post-translational modifications including glycosylation. Native human KNG1 is a glycoprotein; researchers requiring native-like glycosylation patterns should select preparations expressed in mammalian systems.

Can Recombinant Human Kininogen-1 Protein be used in cell-based assays?

Yes, Recombinant Human Kininogen-1 Protein can be used in cell-based assays to study bradykinin receptor signaling (B1R/B2R), cell adhesion, and endothelial responses. For cell-based use, it is essential to use low-endotoxin preparations. Verify endotoxin levels from the CoA before use in cell culture experiments.

What is the difference between HMWK and LMWK isoforms of Kininogen-1?

High-molecular-weight kininogen (HMWK) and low-molecular-weight kininogen (LMWK) are both encoded by the KNG1 gene via alternative splicing but differ in their C-terminal light chain domains. HMWK is the dominant plasma form and serves as a cofactor in contact activation coagulation, whereas LMWK is predominantly involved in tissue kallikrein-mediated kinin generation. Confirm which isoform is represented in rp368842 by consulting the product datasheet.

References

1. Colman RW, Schmaier AH. Contact system: a vascular biology modulator with anticoagulant, profibrinolytic, antiadhesive, and proinflammatory attributes. Blood. 1997;90(10):3819-3843. PMID:9354649
2. Schmaier AH. The contact activation and kallikrein/kinin systems: pathophysiologic and physiologic activities. J Thromb Haemost. 2016;14(1):28-39. PMID:26565070
3. Moreau ME, et al. The kallikrein-kinin system: current and future pharmacological targets. J Pharmacol Sci. 2005;99(1):6-38. PMID:16177542
4. Aladdin Scientific. Recombinant Human Kininogen-1 Protein (rp368842) Product Datasheet. absea#PP-11972.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.