Expanding Your KRAS Workflow with GDP- and GppNHp-Loaded Biotinylated KRAS Proteins

The nucleotide state of KRAS is an important experimental variable in many biochemical and biophysical assays. Depending on the study, researchers may need KRAS in a defined GDP-bound state, an active-state-like conformation, or a flexible format that can be exchanged with a nucleotide selected in-house.

To give researchers more control over this variable, Amid Biosciences has expanded its recombinant KRAS catalog with site-specifically biotinylated proteins supplied in defined nucleotide states.

The new collection includes KRAS G12C, G12D, G12V, and Wild-Type proteins, each available in two formats:

• GDP-loaded KRAS, representing the inactive-state conformation
• GppNHp-loaded KRAS, representing a hydrolysis-resistant, active-state-like conformation

Together, these eight SKUs provide matched nucleotide-state pairs for several of the most widely studied KRAS variants.

Why nucleotide state matters

KRAS functions as a molecular switch. GDP-bound KRAS generally represents the inactive state, while GTP-bound KRAS adopts conformations that support interactions with downstream effectors such as RAF proteins, PI3K, and RalGDS.

For experiments that depend directly on these conformational states, starting with a defined nucleotide-loaded protein can improve assay control and reduce the need for nucleotide exchange and qualification in-house.

GDP-loaded KRAS can be used as an inactive-state reference and as a starting reagent for nucleotide-exchange studies. GppNHp is a hydrolysis-resistant GTP analog commonly used to stabilize an active-state-like KRAS conformation for effector-binding, structural, and screening applications.

Because GppNHp is resistant to hydrolysis, it reduces nucleotide hydrolysis during many binding experiments. For direct measurements of intrinsic or GAP-stimulated GTP hydrolysis, however, KRAS loaded with hydrolyzable GTP should be used instead.

Why site-specific biotinylation?

Site-specific biotinylation enables controlled capture of KRAS on streptavidin- or neutravidin-based assay surfaces. This approach avoids the heterogeneous attachment sites associated with random chemical labeling and supports more consistent comparison between nucleotide states and KRAS variants.

These proteins are particularly suited for surface-based and proximity-based assay formats, including:

• SPR
• BLI
• AlphaLISA and AlphaScreen
• Effector-binding assays
• Active-state and inactive-state binder screening
• Nucleotide-state selectivity studies

Biotinylated KRAS loaded with GDP or GppNHp has been used in SPR workflows to compare nucleotide-dependent interactions and evaluate RAS-binding molecules.

Choosing between standard and nucleotide-loaded KRAS

Our standard recombinant KRAS proteins remain a flexible choice for researchers who perform their own nucleotide exchange, want to use a different nucleotide analog, or do not require a predetermined nucleotide state for their application.

The new GDP- and GppNHp-loaded proteins are designed for workflows in which nucleotide state is a controlled experimental variable and researchers want an assay-ready reagent that reduces preparation and qualification steps.

In practical terms:

• Choose standard recombinant KRAS when experimental flexibility or in-house nucleotide exchange is preferred.
• Choose GDP-loaded KRAS for inactive-state binding studies, exchange assays, and GDP-state controls.
• Choose GppNHp-loaded KRAS for active-state effector binding, state-selective screening, and other assays requiring a stable GTP-like state.

Rather than replacing standard recombinant KRAS, these new formats expand the range of available options so researchers can select the reagent that best fits their experimental workflow.