BioVector® pPIC6 毕赤酵母表达质粒载体

BioVector® pPIC6 Pichia pastoris Expression Plasmid Vector

第一部分 中文说明

一 产品基本信息与遗传学背景

• 载体名称：BioVector® pPIC6 (分 A, B, C 三种阅读框架亚型)

• 产品类型：毕赤酵母（Pichia pastoris）重组蛋白表达质粒载体

• 复制子类型：

  • 大肠杆菌复制子：pUC origin（高拷贝，用于在大肠杆菌中的质粒扩增与克隆）。

  • 酵母整合定位：不含酵母自主复制子（ARS），依靠同源重组整合至毕赤酵母基因组中，实现高度稳定的遗传表达。

• 抗性筛选标记（Dual Selection Markers）：

  • 大肠杆菌筛选：Blastcidin（杀稻瘟菌素抗性基因 bsd），由特异性启动子驱动。

  • 酵母筛选：Blasticidin（杀稻瘟菌素抗性）。该载体利用单一的 Blasticidin（bsd）抗性基因，同时实现大肠杆菌（E. coli）和毕赤酵母（P. pastoris）的双宿主高效选择筛选。

• 分子大小：约 3.4 kb（千碱基对）。

• 生物安全级别：1级（BSL-1）。

二 核心功能元件与转录调控图谱

pPIC6 载体专为在巴斯德毕赤酵母中进行高水平、可诱导性重组蛋白表达而设计。其经典转录调控元件排列如下：

1. AOX1 启动子（5' AOX1 Promoter）：源自毕赤酵母醇氧化酶 1 基因的强启动子。受到甲醇（Methanol）的严格高度诱导调控，在甘油或葡萄糖等碳源中处于完全压制状态，加入甲醇后被极速激活，驱动下游目标蛋白的大规模高效转录。

2. 多克隆位点（MCS）：提供了丰富的内切酶单一切点，并分为 pPIC6 A, B, C 三种变体，每种变体在 MCS 区发生 1-2 个碱基的交错移动，用以方便地将目的基因片段调整至正确的转录翻译阅读框架（Reading frame）内。

3. C-端融合纯化标签（C-terminal Tags）：

   • Myc 标签（Myc Epitope）：便于使用抗 Myc 抗体进行 Western Blot、免疫共沉淀（Co-IP）等常规蛋白质检测。

   • Polyhistidine (6xHis) 标签：位于最末端，便于利用固定化金属亲和层析（IMAC，如 Ni-NTA 磁珠或填料）对重组表达产物进行高纯度一步法提纯。

4. AOX1 转录终止子（3' AOX1 Transcription Terminator）：提供高效的 mRNA 聚腺苷酸化（Polyadenylation）信号和转录终止位点，确保重组 mRNA 的分子稳定性和高效翻译。

5. 整合原理（Genome Integration Mechanism）：在转化毕赤酵母前，质粒需要通过特定的限制性内切酶（如 BstXI 或 PmeI）在 AOX1 启动子区域内进行单切点线性化（Linearization）。线性化后的质粒通过同源重组，以单拷贝或多拷贝的形式插入到酵母基因组的 AOX1 位点上。

三 质粒扩增、转化与酵母筛选标准操作步骤

1. 大肠杆菌中的质粒扩增（Plasmid Propagation）：

   • 推荐宿主：大肠杆菌 TOP10、DH5alpha 或其它常规克隆感受态菌株。

   • 筛选培养基：使用 Low Salt LB 培养基（低盐 LB 固体/液体：含 10 g 胰蛋白胨、5 g 酵母提取物、5 g 氯化钠 NaCl/每升，pH 7.5）。注：Blasticidin 抗生素在常规高盐 LB 培养基中会因离子强度过高而失活，必须严格使用低盐配方。

   • 抗生素工作浓度：大肠杆菌筛选时加入 50 µg/ml 至 100 µg/ml 的杀稻瘟菌素（Blasticidin）。37摄氏度扩增过夜后进行质粒中提或大提。

2. 毕赤酵母重组转化与筛选（Yeast Transformation）：

   • 常用酵母宿主菌株：GS115（His4- 缺陷型菌株）、KM71H、X-33 等。

   • 线性化准备：使用纯化后的质粒，选择 AOX1 启动子内的单一切点酶进行彻底线性化，电泳检查确认完全线性化后，通过苯酚-氯仿抽提或柱纯化回收，溶解于无菌去离子水中。

   • 电转化操作：制备毕赤酵母电转化感受态细胞。将约 5-10 µg 线性化质粒与 80 µl 感受态细胞混合，移入预冷的 0.2 cm 电转杯中。执行毕赤酵母标准电击程序（如 1.5 kV, 25 µF, 200 Ω）。

   • 复苏与铺板筛选：电击后立即加入 1 ml 冰刻的 1 M 山梨醇（Sorbitol）溶液，重悬细胞并置于 30 摄氏度温育复苏 1 到 2 小时。随后将菌液涂布于含有 100 µg/ml 至 300 µg/ml Blasticidin 的 YPD 固体选择性培养基平板上。置于 30 摄氏度恒温培养箱中，静置孵育 3 到 5 天，直至重组整合成功的阳性单菌落生长成熟。

四 核心科研应用方向

1. 胞内高丰度重组蛋白的可诱导性表达：pPIC6 是无分泌信号肽的宿主表达载体，目的蛋白主要积聚在毕赤酵母细胞质（Cytoplasm）中。常用于表达不需要进行复杂糖基化修饰、但在大肠杆菌中易形成包涵体的各种功能性酶类、结构蛋白及可溶性细胞因子的体外大规模制备。

2. 多拷贝重组子的快速高浓度抗生素筛选（Multi-copy Screening）：通过在酵母转化平板中逐步提高 Blasticidin 的抗生素浓度（例如从 300 µg/ml 提高至 1000 µg/ml 甚至更高），可以高效直接地筛选出基因组中发生了多拷贝串联整合（Multi-copy integration）的毕赤酵母超级工程菌株，从而大幅提升目的重组蛋白的终表达产量。

3. 胞内蛋白修饰与体外交互作用纯化研究：利用 C-端内源集成的 Myc 和 6xHis 双标签系统，重组表达的目标蛋白不仅可以用于高纯度的亲和层析提纯，还能直接用于体外蛋白质-蛋白质相互作用（如 Pull-down 实验）、细胞内蛋白质定位分析及质谱学分析研究。

PART 2 ENGLISH SECTION

I General Information and Genetic Background

• Vector Name: BioVector® pPIC6 (Available in three reading frame variants: pPIC6 A, B, and C)

• Product Type: Pichia pastoris heterologous protein expression plasmid vector.

• Replicon Blueprint:

  • E. coli Replicon: pUC origin (High-copy number framework engineered for high-yield propagation in standard bacterial hosts).

  • Yeast Genomic Targeting: Lacks a yeast autonomous replication sequence (ARS). Relies strictly on homologous recombination to stably integrate directly into the Pichia pastoris genome for stable inheritance.

• Dual Selection Marker Framework:

  • Bacterial Selection: Blasticidin resistance (bsd gene) driven by a dedicated prokaryotic promoter sequence.

  • Yeast Selection: Blasticidin resistance. The vector utilizes a single Blasticidin (bsd) resistance marker to achieve high-efficiency selection across both E. coli and P. pastoris expression systems.

• Molecular Size: Approximately 3.4 kb (kilobase pairs).

• Biosafety Level: BSL-1.

II Core Structural Elements and Transcriptional Map

The pPIC6 vector is engineered to drive high-level, methanol-inducible expression of recombinant targets inside Pichia pastoris. The arrangement of its core transcription elements is detailed below:

1. 5' AOX1 Promoter: A strong promoter derived from the Pichia pastoris alcohol oxidase 1 gene. It is tightly regulated and heavily repressed in the presence of carbon sources like glycerol or glucose, but rapidly switches on upon the addition of Methanol to drive heavy transcriptional output.

2. Multiple Cloning Site (MCS): Features a robust selection of unique restriction endonuclease recognition sites. Distributed across three reading frame vectors (pPIC6 A, B, and C), each variant shifts the MCS by 1 or 2 nucleotides to facilitate proper in-frame alignment of the gene of interest with downstream tags.

3. C-terminal Fusion Purification Tags:

   • Myc Epitope Tag: Facilitates rapid Western Blot tracking, immuno-precipitation (IP), and co-IP screening protocols via anti-Myc monoclonal antibodies.

   • Polyhistidine (6xHis) Tag: Positioned at the extreme C-terminus to permit high-purity, one-step purification via Immobilized Metal Affinity Chromatography (IMAC) matrices like Ni-NTA resins.

4. 3' AOX1 Transcription Terminator: Provides essential, efficient mRNA polyadenylation processing signals and precise transcription stop sites to maintain heterologous mRNA stability and translation efficiency.

5. Genomic Integration Mechanism: Prior to transforming Pichia protoplasts or competent cells, the circular vector must undergo complete single-site linearization using unique restriction enzymes (such as BstXI or PmeI) located within the 5' AOX1 promoter sequence. Homologous recombination coordinates the integration of the linear cassette into the host chromosomal AOX1 locus as single or tandem multi-copy arrays.

III Plasmid Propagation, Transformation, and Selection Protocols

1. Bacterial Plasmid Propagation:

   • Recommended Hosts: E. coli TOP10, DH5alpha, or equivalent standard cloning-grade competent cells.

   • Selection Broth Formula: Must use Low Salt LB medium (Low Salt LB broth/agar: 10 g tryptone, 5 g yeast extract, 5 g NaCl per liter, adjusted to pH 7.5). Note: Blasticidin activity is heavily inhibited by high ionic strength; standard high-salt LB recipes will fail to select properly.

   • Antibiotic Working Concentration: Supplement media with 50 µg/ml to 100 µg/ml of Blasticidin for bacterial selection. Culture at 37 degrees Celsius overnight before performing standard plasmid midi- or maxi-preps.

2. Yeast Transformation and Clone Selection:

   • Common Pichia pastoris Strains: GS115 (His4- mutant), KM71H, X-33, and related strains.

   • Linearization Step: Digest the purified plasmid with a unique restriction enzyme inside the 5' AOX1 region. Verify complete linearization via agarose gel electrophoresis, extract with phenol-chloroform or clean with a column system, and resuspend in sterile deionized water.

   • Electroporation Execution: Prepare electrocompetent Pichia pastoris cells. Combine 5-10 µg of the linearized DNA with 80 µl of competent cells, and transfer into a pre-chilled 0.2 cm electroporation cuvette. Pulse using standard yeast parameters (e.g., 1.5 kV, 25 µF, 200 Ω).

   • Outgrowth and Plate Selection: Immediately quench the shocked mixture with 1 ml of ice-cold 1 M Sorbitol solution. Resuspend gently and incubate statically at 30 degrees Celsius for 1 to 2 hours for phenotypic recovery. Plate the slurry onto YPD agar plates supplemented with 100 µg/ml to 300 µg/ml Blasticidin, and incubate at 30 degrees Celsius for 3 to 5 days until positive transformant colonies emerge.

IV Strategic Research Applications

1. Methanol-Inducible Intracellular Production of Recombinant Proteins: As pPIC6 lacks an N-terminal secretion signal peptide sequence, the expressed target accumulates directly within the Pichia cytoplasm. It is widely leveraged for the large-scale production of functional enzymes, structural proteins, and soluble cytokines that do not require complex secretory glycosylation but tend to form insoluble inclusion bodies when expressed in E. coli.

2. Rapid High-Antibiotic Screening for Multi-copy Integrants: By systematically raising selection pressures on YPD plates (e.g., from 300 µg/ml up to 1000 µg/ml or higher Blasticidin levels), investigators can directly enrich hyper-expressing clones carrying tandem multi-copy integration cassettes within their genome, maximizing overall production yields.

3. Protein Modification and Interactome Mapping via Dual Tags: Utilizing the built-in C-terminal Myc and 6xHis fusion framework, the target protein can be purified through affinity chromatography and directly deployed in downstream biochemical assays. These include pull-down assays, intracellular localization tracing via confocal microscopy, and downstream mass spectrometry characterizations.

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