Plasmid Name
pHC-IgG1-K322A
Mutation Set
K322A
Selection Marker
Ampicillin
Promoter
CMV
Fc Engineering Overview
The Human IgG1 (K322A) Fc variant introduces a targeted single amino acid substitution in the CH2 domain designed to selectively abolish C1q binding and complement-dependent cytotoxicity (CDC) while fully retaining native FcγR engagement (ADCC+ / ADCP+) and FcRn-mediated recycling.
Functional Profile
| Property | Effect |
|---|---|
| FcγR binding (I, IIa, IIIa) | Normal / WT Baseline |
| ADCC & ADCP | Normal / WT Baseline |
| CDC | Completely Ablated ↓↓↓ (CDC-Null) |
| FcRn binding | Normal / WT Baseline |
| Serum half-life | Normal / WT Baseline |
| Effector potency | Selective CDC-Null (ADCC+ / ADCP+ / CDCnull) |
Mechanism of Action
The K322A Fc variant replaces lysine at position 322 in the CH2 domain with alanine (Lys322 to Ala). Lysine 322 serves as an essential charged contact point within the core globular C1q binding motif. Disruption of this side-chain interaction eliminates C1q recruitment and downstream complement cascade initiation without altering the structural integrity of the lower hinge or CH2-CH3 domain interfaces responsible for FcγR and FcRn interaction.
Phenotypic Effects
- Complete loss of C1q binding and complement-dependent cytotoxicity (CDC).
- Full retention of native FcγR-mediated effector functions (ADCC and ADCP).
- Eliminates complement-mediated systemic toxicity, cytokine release, or off-target cell lysis.
- Preserves normal FcRn binding, endosomal recycling, and systemic pharmacokinetics.
Applications
- Therapeutic oncology antibodies requiring ADCC/ADCP-driven cell depletion without complement activation.
- Minimizing complement-related side effects in therapeutic antibody development.
- Negative control for evaluating the specific contribution of CDC in target depletion assays.
- Mechanistic dissecting of complement vs. cellular Fc-receptor effector pathways.
Plasmid Map & Feature Annotation
Insert Structure: VH – CH1 – hinge – CH2(K322A) – CH3
- VH: Variable heavy domain
- CH1: Constant heavy 1
- Hinge: Native IgG1 hinge
- CH2(K322A): Selective CDC-ablating single mutation
- CH3: Native IgG1 CH3
Product Note: The K322A mutation is the gold-standard engineering strategy for generating selective CDC-null human IgG1 therapeutics. First identified in landmark alanine-scanning studies, K322A provides surgical elimination of C1q binding while leaving cell-mediated effector mechanisms (ADCC/ADCP) completely intact.
Fusion BioLabs Complement Modulated Family Comparison Matrix
| Variant | Mechanism | Complement Effect | Primary Application & Notes |
|---|---|---|---|
| human IgG1 (WT) Wild-Type |
Native C1q binding | ★★☆☆☆ | Baseline Control. Standard physiological C1q binding and CDC baseline for comparative assays. |
| human IgG1 (HexaBody-Extended) E345K / E430G / E431K |
On-cell hexamerization | ★★★★★+ | Hyper-CDC Enhancer. Triple mutation maximizing Fc-Fc intermolecular interactions; yields ultra-potent C1q avidity against ultra-low density antigen targets. |
| human IgG1 (HexaBody) E345K / E430G |
On-cell hexamerization | ★★★★★ | Canonical CDC-Boosting Fc. Enhances cell-surface hexamer assembly upon antigen binding to drastically boost C1q recruitment and membrane attack complex (MAC) formation. |
| human IgG1 (SEHF) S267E / H268F |
C1q binding loop enhancement | ★★★★☆ | High-Potency CDC Enhancer. Optimizes local electrostatic and structural interactions with C1q to boost complement lysis without requiring hexamerization. |
| human IgG1 (WS) K326W / E333S |
C1q binding loop enhancement | ★★★☆☆ | Strong CDC Enhancer. Synergistic double mutation in CH2 that significantly increases C1q binding affinity and complement killing. |
| human IgG1 (K322A) K322A |
C1q contact site ablation | ★☆☆☆☆ | This Product. Selective Human IgG1 CDC-Null. Abolishes C1q binding and CDC while maintaining native FcγR engagement (ADCC+/ADCP+). |
| human IgG2 (K322A) K322A |
C1q contact site ablation | ★☆☆☆☆ | Completely Silent Human IgG2 Control. Eliminates residual IgG2 C1q binding to yield a fully inert neutralizer (ADCCnull/ADCPnull/CDCnull). |
| mouse IgG2a (CompNull) L235E + E318A / K320A / K322A |
Complement binding triad ablation | ★☆☆☆☆ | Murine CDC-Null Control. Completely abolishes complement activation in murine models while preserving mouse FcγR engagement for syngeneic in vivo studies. |
Storage & Handling
- Store plasmid at −20°C.
- Avoid repeated freeze–thaw cycles.
- Use sterile technique when handling.
- Suitable for transient or stable mammalian expression.
References
- Idusogie EE, Presta LG, Gazzano-Santoro H, Totpal K, Wong PY, Ultsch M, Meng YG, Mulkerrin MG. Mapping of the C1q binding site on rituxan, a chimeric antibody with a human IgG1 Fc. J Immunol. 2000;164(8):4178-4184.
- Hezareh M, Hessell AJ, Jensen RC, van de Winkel JG, Parren PW. Effector function activities of a panel of mutants of a broadly neutralizing antibody against human immunodeficiency virus type 1. J Virol. 2001;75(24):12161-12168.
