サクラゼ-イソマルターゼ複合体: 主要な構造,膜指向,そして,根付いた,内在のブラシ境界タンパク質の進化
Cell
|July 18, 1986
まとめ
研究者らは,ウサギの腸内プロサクラゼ-イソマルターゼ (pro-SI) の構造を決定し,その膜固定とタンパク質挿入における潜在的な二重の役割を明らかにした. この発見は,遺伝子の複製による進化を示唆している.
科学分野:
- バイオケミストリー バイオケミストリー
- 分子生物学は分子生物学である.
- 遺伝学 遺伝学とは
背景:
- 腸内酵素サクラゼ-イソマルターゼ (SI) は,炭水化物の消化に不可欠です.
- その前駆体 (pro-SI) の構造を理解することで,その生体生成と機能の洞察が得られます.
研究 の 目的:
- ウサギの腸内プロサクラゼ-イソマルターゼ (pro-SI) の完全な原発構造を決定する.
- 膜固定と触媒領域に関連する構造的特徴を解明する.
主な方法:
- ほぼ全長cDNA配列から主構造の推論.
- 推論されたアミノ酸配列のバイオ情報分析.
主要な成果:
- ウサギの腸内プロ-SI (1827アミノ酸) の完全な主構造が決定されました.
- Pro-SIは,単一の20アミノ酸の膜横断セグメントと12アミノ酸のN端のサイトプラズマ領域を特徴としています.
- セリン/スレオニンに富んだ茎領域は,膜アンカーを触媒ドメインに接続し,サクラゼとイソマルターゼの部分の間には41%のアミノ酸同一性があります.
結論:
- 膜を横断するセグメントは,膜挿入のための未開の信号として機能する可能性があります.
- プロ-SI構造は,部分的な遺伝子複製による進化を示唆しています.
- 推論された構造は,プロSIの機能と規制を理解するための基礎を提供します.
関連する概念動画
Carbohydrate Digestion
Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. Carbohydrate digestion starts in the mouth during mastication, or chewing. The masticated carbohydrates remain intact in the stomach. Digestion resumes in the duodenum of the small intestine, where pancreatic alpha-amylase and brush border enzymes of the microvilli convert complex carbohydrates to monosaccharides. Finally, the monosaccharides...
Protein and Protein Structure
Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective. They may serve in transport, storage, or membranes; or they may be toxins or enzymes. Their structures, like their functions, vary greatly. They are all, however, amino acid polymers arranged in a linear sequence.
A protein's shape is critical to its function. For example, an enzyme can...
A protein's shape is critical to its function. For example, an enzyme can...
Oligosaccharide Assembly
Protein glycosylation starts in the ER lumen and continues in the Golgi apparatus. Glycosyltransferases catalyze the addition of sugar molecules or glycosylation of proteins. Usually, these enzymes add sugars to the hydroxyl groups of selected serine or threonine residues to form O-linked glycans or the amino groups of asparagine residues to form N-linked glycans. Different positions on the same polypeptide chain can contain differently linked glycans.
Multiple sugar molecules that may or may...
Multiple sugar molecules that may or may...
Insertion of Multi-pass Transmembrane Proteins in the RER
The rough ER membrane synthesizes, assembles, and embeds transmembrane proteins in diverse topologies. These proteins function as transporters or channels and can remain in the ER membrane or are sent to the Golgi complex, lysosome, and cell membrane.
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
Multi-pass Transmembrane Proteins and β-barrels
In multi-pass transmembrane proteins, the polypeptide chain crosses the membrane more than once. The transmembrane polypeptide chain either forms an α-helix or β-strand structure. α-Helix containing multi-pass transmembrane proteins are ubiquitous, whereas β-strand containing ones are mainly found in gram-negative bacteria, mitochondria, and chloroplasts.
α-Helix containing multi-pass transmembrane proteins
Multi-pass transmembrane proteins such as G-protein-linked receptors (GPCRs) and...
α-Helix containing multi-pass transmembrane proteins
Multi-pass transmembrane proteins such as G-protein-linked receptors (GPCRs) and...
Protein Translocation Machinery on the ER Membrane
The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.


