SV40 Nuclear Transport Signal Peptide Analog is a 13-amino-acid synthetic nuclear-targeting peptide containing the classical PKKKRKV nuclear localization motif from SV40 large T antigen within an extended sequence.

The AS2737 sequence, CGYGPKKKRKVGG, differs functionally from a minimal SV40 NLS because it includes additional flanking residues and an N-terminal cysteine. This cysteine provides a practical chemical handle for conjugating the NLS-containing peptide to compatible proteins or other research cargos.

The design is particularly relevant when nuclear targeting needs to be studied in the context of a covalently attached molecule rather than as an isolated short peptide.

Product Information

A Conjugation-Ready SV40 NLS Format

One of the most experimentally useful differences between AS2737 and a minimal NLS sequence is the N-terminal cysteine.

The thiol group of cysteine can provide a defined reactive site for appropriate conjugation chemistries. This allows researchers to attach an NLS-containing peptide to a protein, macromolecular construct, or another compatible experimental cargo while preserving the basic SV40 targeting motif within the peptide.

This format can be advantageous when a study requires control over the attachment site rather than nonspecific modification of multiple lysine residues.

Historical Use in Carrier-Protein Nuclear Transport

Synthetic peptides containing the SV40 large T-antigen transport sequence were among the earliest systems used to demonstrate that a short peptide signal could direct an attached carrier toward the nucleus.

Experiments with 13-residue SV40-related peptides showed nuclear transport after covalent attachment to carrier proteins. The efficiency depended not only on the NLS itself but also on factors including peptide density and cargo properties.

AS2737 is therefore particularly relevant to NLS–cargo conjugation studies, rather than being simply a longer version of the minimal SV40 sequence.

Sequence Architecture

The AS2737 sequence is:

CGYGPKKKRKVGG

Within this sequence:

PKKKRKV represents the classical SV40 NLS core.

The surrounding CGYG and GG residues create an extended sequence context, while the N-terminal cysteine provides a potential conjugation handle.

This distinction matters experimentally because flanking residues, attachment geometry, and exposure of the NLS can influence recognition by the nuclear import machinery.

Researchers who require different spacers, additional cysteines, terminal modifications, fluorescent labels, or alternative attachment sites can use our Custom Peptide Synthesis service to develop related constructs.

Nuclear Transport versus Cell Entry

Nuclear localization and plasma-membrane penetration are separate biological steps.

An NLS primarily provides information for nuclear-import machinery after the NLS-bearing cargo is available to the cytoplasmic transport system. Researchers designing a complete intracellular delivery experiment should therefore distinguish cellular uptake from subsequent nuclear targeting.

When both functions are needed, an NLS may be studied together with an independent cell-entry strategy. Researchers exploring peptides designed primarily for cellular internalization can also view our Cell-Penetrating Peptides (CPPs) collection.

This distinction is particularly important when interpreting apparent nuclear accumulation in different cell models or delivery systems.

Experimental Design Considerations

Cargo size, NLS copy number, linker length, conjugation site, peptide accessibility, and intracellular availability can all influence the behavior of an NLS conjugate.

For this reason, the presence of the PKKKRKV motif should not be treated as a guarantee of identical nuclear transport across different cargos. Matched controls using unconjugated cargo, alternative attachment positions, or a modified NLS sequence can provide more informative comparisons.

For a more compact reference sequence, researchers can compare AS2737 with SV40 NLS (AS2736).

Quality Considerations for Conjugation Studies

For conjugation-based workflows, peptide identity and purity are particularly important because impurities containing truncated or altered N-terminal sequences can behave differently during coupling.

Mass spectrometry supports confirmation of expected molecular identity, while analytical HPLC provides chromatographic purity information. Batch-specific characterization can be reviewed through our Peptide Quality Control capabilities.

After peptide conjugation, researchers should characterize the final conjugate separately because peptide QC alone does not establish conjugation efficiency or final cargo functionality.

Storage and Handling

Store lyophilized AS2737 according to the supplied batch documentation and protect it from moisture.

When the N-terminal cysteine is intended for downstream conjugation, handling conditions should minimize unnecessary oxidation before the coupling step.

Research Use Only

SV40 Nuclear Transport Signal Peptide Analog is supplied for research use only. It is not intended for therapeutic, or human use.