Bsa I (RNase-free): Practical DNA Cleavage Guide

Bsa I (RNase-free) is a recombinant mutant protein expressed in Escherichia coli and derived from the BsaI gene of Bacillus stearothermophilus. As a type IIS restriction endonuclease, it recognizes the sequence 5′-GGTCTC(N)-3′ and cleaves at a defined position downstream of that recognition sequence. This separation between recognition and cleavage sites is useful when designing controlled DNA ends for cloning and other DNA recombinant technology workflows.

The product is supplied with 10X Cut rA Buffer. Its RNase-free formulation is intended to minimize RNA degradation during sensitive nucleic acid manipulations, although the entire workflow must also be protected from RNase contamination. The Bsa I (RNase-free) product information lists 1000 U, 5000 U, and 10000 U options and storage at -80 °C. APExBIO identifies the product for scientific research use only.

What This Product Solves

Many cloning workflows require DNA cleavage at a predictable sequence while retaining control over the sequence of the resulting DNA ends. Bsa I addresses this requirement by recognizing a defined site and cutting downstream from it, making it suitable for planned gene cloning, modular DNA assembly, and other DNA manipulation tasks. The cleavage site should be treated as a design parameter rather than inferred solely from the recognition motif.

The RNase-free format is useful when DNA cleavage is performed alongside RNA-sensitive work, such as workflows that preserve RNA-containing samples or proceed directly into nucleic acid analysis. It does not make an entire laboratory workflow RNase-free by itself. Tubes, water, pipette tips, buffers, handling surfaces, and downstream reagents can still introduce RNase.

For related sequence-directed cleavage guidance, see Bsa I (RNase-free): Practical DNA Cleavage Guide; it provides complementary context on cloning-oriented use and research-only boundaries. For a related handling perspective, see Bsa I (RNase-free): Technical Guidance for DNA Manipulation; it focuses on RNA-sensitive processing and RNase-free laboratory practice.

Protocol Parameters

The following product values are taken from the supplied dossier. Reaction volume, enzyme amount per reaction, incubation duration, and any inactivation or cleanup conditions should be taken from the current product instructions or established in a local validation experiment rather than assumed from this article.

• Assay: Recognition sequence; Value: 5′-GGTCTC(N)-3′; Applicability: substrate and construct design; Rationale: confirm that the intended DNA molecule contains the required recognition sequence in the correct orientation and context; Evidence basis: product dossier.
• Assay: Enzyme class; Value: type IIS restriction endonuclease; Applicability: sequence-directed DNA cleavage and cloning design; Rationale: cleavage occurs at a defined position downstream of the recognition sequence, so junction design must account for both the motif and downstream cut site; Evidence basis: product dossier.
• Assay: Reaction buffer; Value: supplied 10X Cut rA Buffer; Applicability: routine enzymatic digestion setup; Rationale: use the supplied buffer according to the current instructions to provide the intended reaction environment; Evidence basis: product dossier.
• Assay: Storage; Value: -80 °C; Applicability: long-term product storage; Rationale: maintain the listed storage condition to support product stability and activity; Evidence basis: product dossier.
• Assay: Available unit sizes; Value: 1000 U, 5000 U, and 10000 U; Applicability: experiment planning and inventory control; Rationale: select a package size based on the validated digestion frequency and expected project duration; Evidence basis: product dossier.
• Assay: Nuclease formulation; Value: RNase-free; Applicability: RNA-sensitive nucleic acid workflows; Rationale: minimize RNA degradation attributable to the enzyme preparation while maintaining RNase-free handling throughout the procedure; Evidence basis: product dossier.

Workflow Setup and QC Checklist

Before the reaction

• Inspect the target sequence in both strands and confirm the complete 5′-GGTCTC(N)-3′ recognition motif. Map all intended and unintended sites before digesting a plasmid, PCR product, or donor fragment.
• For cloning or assembly, define the desired junctions in silico and verify that cleavage downstream of the recognition sequence produces the intended DNA ends. Do not design junctions from the recognition motif alone.
• Retrieve the current instructions for K1095 and record the required enzyme amount, reaction volume, incubation conditions, and any recommended post-digestion treatment in the laboratory worksheet.
• Keep the enzyme and buffer handled according to the product instructions, and avoid unnecessary warming or repeated handling. Use clean, nuclease-controlled consumables for RNA-sensitive experiments.

During and after digestion

• Prepare a substrate-only control and, when practical, an enzyme-containing control using a DNA substrate with a known cleavage outcome. These controls help distinguish substrate problems from reagent or setup problems.
• Mix without introducing bubbles, briefly collect liquid from tube walls, and use a consistent order of addition across samples. Do not add unvalidated salts, detergents, or competing buffers.
• Assess the digest using an appropriate DNA analysis method. Compare the treated sample with the untreated control and interpret partial digestion, multiple fragments, or unchanged substrate in relation to the sequence map.
• If the digest feeds gene cloning or another assembly step, remove or dilute reaction components as required by the downstream method and verify that the DNA ends remain compatible with the planned construct.

Common Failure Modes and Fixes

No visible cleavage or incomplete digestion

First recheck the recognition sequence, strand orientation, and substrate identity. A missing site, a sequence mutation, inaccessible template structure, degraded enzyme, incorrect buffer, or inhibitors carried over from purification can all produce an unchanged or partially changed DNA pattern. Confirm storage history, use the supplied buffer, and repeat the reaction with a clean control substrate before increasing enzyme input or changing multiple variables at once.

Unexpected fragment pattern

Unexpected bands may reflect additional Bsa I sites, an incorrect in-silico map, partial digestion, mixed PCR products, or nonspecific DNA damage introduced during sample preparation. Re-sequence or remap the substrate, include an untreated control, and compare the observed pattern with the predicted cleavage map. Avoid assigning a fragment identity from gel position alone.

RNA degradation in an RNA-sensitive workflow

The RNase-free formulation reduces risk from the enzyme preparation but does not protect against contaminated water, tubes, tips, gloves, benches, or downstream reagents. Use dedicated RNase-controlled materials, change gloves after contact with shared surfaces, and keep RNA handling physically separated from ordinary DNA work. If degradation persists, test the other workflow components individually rather than assuming the restriction enzyme is the source.

Cloning or assembly fails after apparently successful digestion

Successful cleavage does not confirm that the intended junctions, fragment orientation, reading frame, or vector-to-insert compatibility are correct. Recheck the complete construct design, including the downstream cleavage position and any bases retained at the junction. Confirm DNA concentration and purity, use a validated ligation or assembly setup, and sequence the final construct rather than relying only on colony screening.

Scope and Limitations

This guidance is based on the product dossier and general laboratory workflow practice; no directly matched paper evidence or study-specific performance data are being asserted here. The dossier specifies the enzyme identity, recognition sequence, downstream cleavage behavior, supplied buffer, RNase-free formulation, unit sizes, storage condition, and research-use limitation, but it does not establish universal reaction conditions for every DNA substrate.

Accordingly, do not infer reaction volumes, incubation times, temperature profiles, heat-inactivation conditions, or detection limits from this article. Confirm those parameters against the current instructions and validate them with the actual substrate. The product is not intended for diagnostic, clinical, medical, or therapeutic use.

Conclusion

Bsa I (RNase-free), SKU K1095, is a practical DNA cleavage enzyme for sequence-planned cloning and DNA manipulation where downstream cleavage and reduced RNase risk are important. Reliable use depends on accurate sequence mapping, correct buffer selection, controlled nuclease handling, appropriate controls, and independent verification of the final DNA product.