BioVector® pNK1508 Yeast Autoconvertible Bioluminescence Toolkit Vector / pNK1508 真酵母自主发光合成通路核心组件质粒

一 产品基本信息与分子生物学背景

• 质粒名称：pNK1508。

• 载体类型与应用系统：真核/真菌表达质粒（Yeast Expression Vector）。

  pNK1508 是现代合成生物学中构建“真核生物自主发光系统（Autonomous Eukaryotic Bioluminescence System）”的核心工具质粒。该发光系统转化自高等真菌（如 Neonothopanus nambi 毒蘑菇）的生物发光基因通路（Fungal Bioluminescence Pathway, FBP）。在真菌发光通路中，底物咖啡酸（Caffeic acid）需要在多种关键酶的连续催化下，生成发光前体“发光素（Hispidin）”，再经羟化和荧光素酶催化产生持续稳定的自发荧光。然而，其中的核心限速酶——发光素合酶（Hispidin Synthase, HispS）是一种复杂的聚酮合酶（PKS），它的激活绝对依赖于转录后的4'-磷酸泛酰巯基乙胺化修饰（4'-phosphopantetheinyl transferase, PPTase）。为了使该系统能够在酿酒酵母（Saccharomyces cerevisiae）等异源真核宿主中高效运转，研究人员构建了 pNK1508 载体。该载体专门用来高水平过表达源自构巢曲霉（Aspergillus nidulans）的 PPTase 广谱激活酶——NpgA。

• 基因/插入片段构型（核心元件图谱）：

  • 启动子（Promoter）：启动子采用强效的 pGAP（Glyceraldehyde-3-phosphate dehydrogenase promoter） 组成型启动子。在酵母体内无需添加外源诱导剂（如半乳糖），即可在对数生长期和维持期持续提供高强度的基因转录。

  • 目的基因（Insert Gene）：构巢曲霉源 4'-磷酸泛酰巯基乙胺转移酶基因 NpgA（来自 Aspergillus nidulans），片段大小约为 1039 bp。它能精确对异源表达的真菌发光素合酶（HispS）实施翻译后修饰与化学激活。

  • 终止子（Terminator）：下游搭载高稳定性酵母 tAOX（Alcohol oxidase terminator） 终止子序列，确保 mRNA 的精确裁剪和翻译扩增稳定性。

• 克隆与筛选构型（骨架特征）：

  • 骨架大小：不含目的基因的载体骨架约为 3503 bp。

  • Golden Gate 兼容性：基于高级通用模块化克隆技术（MoClo/Golden Gate）原理设计，能与生物发光通路的其它组件（如 pNK5867 发光素合酶质粒、pNK5712 羟化酶质粒、pNK5785 荧光素酶质粒等）形成完美模块化组合。

  • 真核筛选标记（Yeast Selection）：携带潮霉素（Hygromycin B）抗性标记，在酵母转化筛选中通常添加 $200\ \mu\text{g/mL}$ 潮霉素进行正向压选。

  • 原核筛选标记（Bacterial Resistance）：大肠杆菌筛选阶段同样依靠骨架自带的 Hygromycin 或者是氨苄青霉素/特定广谱筛选标记（依据不同亚型扩增）。

二 核心科研价值与合成生物学/分子成像应用

pNK1508 作为真菌生物发光异源重建的“开关型辅因子元件”，在以下前沿领域中扮演核心角色：

1. 构建“不依赖外源底物”的自主发光酵母（Autonomous Bioluminescent Yeast）：

   传统荧光素酶报告系统（如 Firefly Luciferase）必须在检测前向体系中注入昂贵且穿透力有限的底物（如 D-luciferin）。通过将 pNK1508 与真菌发光通路的其他 4 个核心基因联合转化酵母，可使酵母直接利用自身代谢产物咖啡酸实现体内自发光（无需添加任何底物，即开即用）。

2. 活体实时动态监测与药物高通量筛选（Real-time In Vivo Imaging）：

   用于环境毒素监测、真菌感染模型动力学追踪。由于该系统是完全自主发光，科研人员可以无创地、连续数天甚至数周在成像仪下观察酵母群落的物理空间迁移、生长状态演变，特别适用于微流控芯片、活体组织深层的无底物干扰荧光动态捕捉。

3. PKS / NRPS 酶学活化机制的底层改造研究：

   NpgA 作为一种功能极其强大的广谱 PPTase，不仅能激活发光系统的 HispS，还能激活其他大量异源表达的聚酮合酶（PKS）和非核糖体肽合成酶（NRPS）。pNK1508 是研究次级代谢产物人工合成、新型天然抗生素底盘改造的经典辅助质粒。

三 实验室大肠杆菌扩增、质粒提取质控与酵母转化标准步骤

1. 大肠杆菌中的质粒扩增、保种与提取

• 推荐宿主感受态：大肠杆菌 DH5$\alpha$（或 Top10 级高克隆丰度感受态细胞）。

• 菌落抗生素选择压力：大肠杆菌培养基中添加 $200\ \mu\text{g/mL}$ 潮霉素（Hygromycin B）（依据质粒骨架构建说明，部分衍生骨架可能兼容 Ampicillin，但通用质控以载体自带的抗性为准）。

• 操作流线：

  1. 取 1 - 2 $\mu$L 的 pNK1508 质粒 DNA 投入 50 $\mu$L 的 DH5$\alpha$ 感受态细胞中，冰置 30 分钟。

  2. 42 ℃ 热激 45 - 60 秒，立刻放回冰上静置 2 分钟。

  3. 加入 250 $\mu$L 无抗生素的 LB 液体培养基，37 ℃、220 rpm 振荡复苏 60 分钟（让潮霉素抗性基因充分表达）。

  4. 取 100 $\mu$L 菌液涂布于含有 200 $\mu$g/mL 潮霉素的 LB 琼脂平板上，37 ℃ 倒置培养 16 - 18 小时直至长出单菌落。

  5. 挑取丰满单菌落接入 5 mL 含药 LB 液体培养基中，37 ℃、250 rpm 摇菌过夜（12 - 14h）。

  6. 保种与提质粒：吸取 800 $\mu$L 菌液加 200 $\mu$L 灭菌甘油，摇匀后置于 -80 ℃ 冰箱长期保种。其余菌液使用标准商业化质粒抽提试剂盒（Miniprep Kit）提取高纯度质粒 DNA。

2. 质粒分子量验证与纯度质控红线（Quality Control Guidelines）

在进行下游酵母转化前，必须通过双电泳或酶切、测序对质粒实施严格的质量把关：

• 浓度与纯度测定：利用 NanoDrop 分光光度计测定。质控红线：$OD_{260}/OD_{280} = 1.8 - 2.0$ 之间，吸光度曲线正常；质粒终浓度推荐 $\ge 200\text{ ng/}\mu\text{L}$，确保无大肠杆菌基因组 DNA 或 RNA 污染。

• 限制性内切酶切/Golden Gate 酶切验证（电泳带谱分析）：

  使用具有单切或双切位点的内切酶对 pNK1508 进行酶切验证。酶切产物在 1% 琼脂糖凝胶电泳中运行，质控标准带谱：应清晰出现一条约 3503 bp 的骨架条带以及一条约 1039 bp 的 NpgA 插入片段条带。条带位置完全吻合方可进入转化流线。

• 测序引物推荐：

  • 5′ 正向测序引物：5'-cctaggaaattttactctgctgga-3'

  • 3′ 反向测序引物：5'-gcaaatggcattctgacatcc-3'

3. 酿酒酵母（S. cerevisiae）的化学转化与抗性筛选步骤（醋酸锂法）

为了在酵母体内表达 NpgA 蛋白，经典的醋酸锂（LiAc/PEG）介导转化法流程如下：

1. 酵母前培养：挑取酵母宿主菌落（如 BY4741 或 YPH499 菌株）接入 5 mL YPD 液体培养基中，30 ℃ 振荡培养过夜。

2. 对数扩增：按 1:10 比例将过夜菌转接至 50 mL 新鲜 YPD 中，30 ℃ 培养 3 - 5 小时，直至 $OD_{600}$ 达到 0.6 - 0.8（处于最活跃的分裂中期）。

3. 洗涤沉淀：以 3000 rpm 离心 5 分钟收集酵母菌体，用 25 mL 无菌无离子水洗涤 1 次，离心弃上清；再用 1 mL 新鲜配制的 0.1 M LiAc（醋酸锂）溶液 重悬菌体，转移至 1.5 mL 离心管中，高速离心 30 秒，抽干上清。

4. 配制转化混合物（Transformation Cocktail）：向管底的酵母菌泥中，严格按照以下顺序依次叠加加入组分：

   • 240 $\mu$L 50% PEG 3350 溶液

   • 36 $\mu$L 1.0 M LiAc 溶液

   • 25 $\mu$L 预先热变性（95 ℃加热5分钟后立刻冰浴）的单链载体 DNA（Salmon Sperm DNA, 2 mg/mL）

   • 5 - 10 $\mu$L 抽提好的 pNK1508 质粒 DNA（约合 1 - 2 $\mu$g）

5. 重悬与热激：用枪头极其轻柔地吹打混匀该混合物（注意：PEG 溶液极度黏稠，需彻底吹匀），随后置于 30 ℃ 恒温水浴箱中静置孵育 30 分钟。

6. 热休克释放：随后将离心管整体移入 42 ℃ 水浴箱中，精确执行热激 15 - 20 分钟。

7. 复苏与铺板（关键抗性红线）：

   12000 rpm 快速离心 30 秒，小心吸干上清。注意：潮霉素（Hygromycin B）属于杀菌型抗生素，热激后的酵母绝对不能直接涂布于含药平板上！ 必须向管底加入 1 mL 新鲜 YPD 液体培养基，置于 30 ℃ 摇床中、150 rpm 温和复苏培养 2 - 3 小时，让酵母质膜上的潮霉素抗性磷酸转移酶（HPH）蛋白得到充分翻译和组装。

8. 离心收集复苏后的菌体，用 100 $\mu$L 无菌水重悬，全量涂布于含有 $200\ \mu$g/mL 潮霉素 B 的 YPD 固体选择性琼脂平板上。

9. 置于 30 ℃ 恒温孵箱中静置培养 48 - 72 小时，待平板上长出饱满、边缘规整的转化子阳性单菌落。

4. 协同基因表达与自主发光质检规范

• 联合验证：获得 pNK1508（表达 NpgA）表达株后，需将发光通路的其他质粒依次导入或共转化。

• 发光功能质检：在黑暗环境下，使用高灵敏度冷 CCD 成像仪或微孔板发光仪（Luminometer）直接测定转化子菌落。若在未添加任何外源底物的情况下，酵母群落表现出持续、高对比度的内源自发性绿色生物发光（中心波长约 520 nm），且发光强度明显高于未转化 pNK1508 的对照组，说明 NpgA 转移酶已成功激活 HispS，该真核自主发光系统构建成功。

Part 2 English Section

I Product General Information and Molecular Background

• Plasmid Nomenclature: pNK1508.

• Vector Type and Expression Framework: Eukaryotic / Yeast Expression Vector.

  The pNK1508 platform represents a vital molecular component engineered to establish an "Autonomous Eukaryotic Bioluminescence System" within heterologous fungi. This expression matrix adapts genes from the Fungal Bioluminescence Pathway (FBP) derived from bioluminescent macrofungi like Neonothopanus nambi. In this fungal system, the precursor caffeic acid undergoes sequential enzymatic breakdown to form the key intermediate "hispidin" (the fungal luciferin), which then emits sustained luminescence via enzymatic oxidation.

  However, the rate-limiting enzyme—Hispidin Synthase (HispS), a complex Polyketide Synthase (PKS)—requires post-translational activation. It must undergo 4'-phosphopantetheinyl transferase (PPTase) modification to convert from its inactive apo-form into its active holo-form. To facilitate this modification in heterologous systems like Saccharomyces cerevisiae, researchers engineered pNK1508 to direct high-level, constitutive expression of NpgA, a highly broad-spectrum PPTase from Aspergillus nidulans.

• Expression Cassette Configuration (Core Genetic Architecture):

  • Promoter: Driven by the robust, continuous pGAP (Glyceraldehyde-3-phosphate dehydrogenase) promoter. This sequence drives strong, constitutive transcription throughout the active log phase and stationary survival windows in yeast without requiring chemical inducing agents (e.g., galactose).

  • Gene/Insert: The Aspergillus nidulans 4'-phosphopantetheinyl transferase gene, NpgA, spanning approximately 1039 bp. It mediates the post-translational phosphopantetheinylation required to unlock heterologous fungal HispS activity.

  • Terminator: Terminated by a high-stability yeast tAOX (Alcohol oxidase) transcription terminator sequence to guarantee clean mRNA processing and protect translational throughput.

• Cloning Coordinates and Selectable Footprint:

  • Backbone Dimensions: Modulates a standalone base vector size of approximately 3503 bp excluding the expression insert.

  • Golden Gate Compatibility: Built to integrate with Level 1-like modular assembly frameworks (MoClo), allowing seamless combination with other bioluminescent circuit modules (e.g., pNK5867 encoding HispS, pNK5712 encoding hydroxylase, or pNK5785 encoding luciferase).

  • Yeast Selection Coordinate: Outfitted with a eukaryotic Hygromycin B selection marker, routinely selected in transgenic yeast protocols using $200\ \mu\text{g/mL}$ Hygromycin B.

  • Bacterial Selection Coordinate: Amplified across competent Escherichia coli steps utilizing the backbone's integrated Hygromycin resistance cassette (or ampicillin variations depending on clonal subtyping modifications).

II Strategic Research Value and Synthetic Biology Applications

The pNK1508 vector functions as an indispensable post-translational switch for heterologous bioluminescence reconstruction and metabolic engineering:

1. Engineering "Substrate-Free" Living Luminescent Reporters:

   Traditional luciferase systems (such as firefly luciferase) require the addition of costly, chemically restricted substrates (e.g., D-luciferin) before imaging. Co-transforming pNK1508 alongside the other 4 core fungal bioluminescence components allows yeast to tap into internal caffeic acid pools, enabling substrate-independent autoluminescence that eliminates the need for external chemical reagents.

2. Real-Time Dynamic In Vivo Imaging and High-Throughput Screenings:

   Ideal for biosensor engineering, toxicity screens, and in vivo tracking of fungal infection dynamics. Because the system is completely autonomous, investigators can perform continuous, non-invasive imaging across days or weeks, making it well-suited for microfluidic assays and deep-tissue imaging where substrate delivery is a barrier.

3. Deciphering PKS / NRPS Activation Cascades:

   As a broad-spectrum PPTase, NpgA can activate a wide array of heterologous Polyketide Synthases (PKS) and Non-Ribosomal Peptide Synthetases (NRPS) beyond the fungal hispidin system. This makes pNK1508 a versatile tool for studying secondary metabolite synthesis and engineering novel biosynthetic pathways.

III Laboratory Bacterial Propagation, Quality Control, and Yeast Transformation Protocols

1. Plasmid Amplification and Isolation in Escherichia coli

• Recommended Competent Host Strain: Escherichia coli DH5$\alpha$ (or high-efficiency Top10 cloning alternatives).

• Antibiotic Selection Matrix: Supplement standard LB media with $200\ \mu\text{g/mL}$ Hygromycin B (verify specific backbone updates, as some derivatives may introduce ampicillin selection parameters; however, default tracking relies on the core hygromycin marker).

• Execution Workflow:

  1. Dispense 1 – 2 $\mu$L of pure pNK1508 plasmid DNA into a 50 $\mu$L aliquot of competent DH5$\alpha$ cells; incubate on ice for 30 minutes.

  2. Heat-shock the mixture at 42 °C for 45 – 60 seconds, then transfer back to ice for 2 minutes.

  3. Introduce 250 $\mu$L of nutrient-rich, antibiotic-free LB broth and recover at 37 °C with shaking at 220 rpm for 60 minutes to allow the antibiotic resistance markers to express.

  4. Plate a 100 $\mu$L volume of the recovered culture onto selective LB agar plates fortified with 200 $\mu$g/mL Hygromycin B. Incubate inverted at 37 °C for 16 – 18 hours.

  5. Inoculate a single isolated colony into 5 mL of selective LB broth and grow at 37 °C with shaking at 250 rpm overnight (12 – 14 hours).

  6. Preservation and Extraction: Blend an 800 $\mu$L aliquot of the culture with 200 $\mu$L of sterile glycerol to prepare -80 °C permanent cryogenic stocks. Process the remaining culture fluid with a commercial miniprep kit to isolate high-purity plasmid DNA.

2. Plasmid Profiling and Quality Control Metrics

Prior to initializing yeast engineering protocols, validate the structural integrity of the extracted plasmid via spectrophotometry and restriction digest mapping:

• Concentration and Purity Parameters: Measure optical density via a NanoDrop spectrophotometer. Quality Control Standard: Acceptable $OD_{260}/OD_{280}$ ratios must fall between 1.8 and 2.0. Ensure the clean absence of genomic DNA or RNA contaminants, aiming for a concentration threshold $\ge 200\text{ ng/}\mu\text{L}$.

• Restriction Enzyme Verification Mapping (Electrophoresis Fingerprinting):

  Perform a restriction digest (or Golden Gate analytical cut) to linearize the plasmid. Resolve the digested fragments on a 1% agarose gel. Quality Control Target Bands: The gel profile must cleanly display a backbone fragment migrating at approximately 3503 bp and an NpgA insert band migrating at 1039 bp. Proceed to downstream transformation loops only if the bands match these sizes perfectly.

• Recommended Sequencing Primers:

  • 5′ Forward Primer: 5'-cctaggaaattttactctgctgga-3'

  • 3′ Reverse Primer: 5'-gcaaatggcattctgacatcc-3'

3. Lithium Acetate (LiAc/PEG) Transformation Matrix for S. cerevisiae

To achieve robust expression of NpgA in yeast, execute the standard Lithium Acetate (LiAc/PEG-3350) chemical transformation protocol:

1. Pre-Cultivation: Inoculate the chosen yeast strain (e.g., BY4741 or YPH499) into 5 mL of standard YPD broth and grow at 30 °C with shaking overnight.

2. Log-Phase Amplification: Dilute the overnight culture 1:10 into 50 mL of fresh YPD broth. Incubate at 30 °C with shaking for 3 – 5 hours until the $OD_{600}$ reaches 0.6 – 0.8 (targeting mid-log phase cells).

3. Harvest and Conditioning: Spin down the yeast biomass at 3000 rpm for 5 minutes. Wash the pellet once with 25 mL of sterile deionized water, pellet again, and resuspend in 1 mL of freshly prepared 0.1 M LiAc solution. Transfer the slurry to a 1.5 mL tube, spin at maximum speed for 30 seconds, and thoroughly aspirate the supernatant.

4. Assembly of the Transformation Cocktail: Add the following components to the yeast pellet strictly in the order listed:

   • 240 $\mu$L of sterile 50% w/v PEG 3350 solution

   • 36 $\mu$L of sterile 1.0 M LiAc solution

   • 25 $\mu$L of pre-boiled and chilled single-stranded carrier DNA (Carrier Carrier Salmon Sperm DNA, 2 mg/mL)

   • 5 – 10 $\mu$L of purified pNK1508 plasmid DNA (equivalent to ~1 – 2 $\mu$g)

5. Homogenization: Vortex or pipette the dense mixture gently until the pellet is completely resuspended. (Note: PEG is highly viscous; ensure thorough blending). Incubate statically at 30 °C for 30 minutes.

6. Heat Shock: Transfer the transformation assembly directly into a 42 °C water bath and incubate for exactly 15 – 20 minutes.

7. Outgrowth Phase (Critical Selective Pressure Boundary):

   Centrifuge at 12,000 rpm for 30 seconds and aspirate the supernatant. CRITICAL STEP: Because hygromycin B is a bactericidal antibiotic, heat-shocked yeast cannot be plated directly onto selective media. Resuspend the pellet in 1 mL of fresh, antibiotic-free YPD broth and incubate at 30 °C with shaking at 150 rpm for 2 – 3 hours of outgrowth. This allows the newly introduced hygromycin phosphotransferase (HPH) enzyme to be transcribed and translated.

8. Pellet the recovered cells, resuspend in 100 $\mu$L of sterile water, and plate the entire volume onto selective YPD agar plates supplemented with 200 $\mu$g/mL Hygromycin B.

9. Incubate inverted at 30 °C for 48 – 72 hours until robust, clear colonies appear on the plate.

4. Co-Expression Validation and Luminescence Screening

• Functional Validation: Once pNK1508 is established in the yeast host, the remaining components of the pathway must be introduced via sequential transformation or co-transformation protocols.

• Luminescence Quality Control: Image the engineered colonies using a high-sensitivity cooled CCD camera or evaluate them with a microplate luminometer in a darkroom environment. The success of the pNK1508 vector integration is verified by the observation of sustained, endogenous green bioluminescence ($\lambda_{max} \approx 520\text{ nm}$) without the addition of any external substrates, showing a significantly higher signal compared to control strains lacking NpgA expression.

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