8EIM

Structure of ALAS with C-terminal truncation from S. cerevisiae

8EIM の概要

• エントリーDOI: 10.2210/pdb8eim/pdb
• 分子名称: 5-aminolevulinate synthase, mitochondrial, PYRIDOXAL-5'-PHOSPHATE, GLYCEROL, ... (5 entities in total)
• 機能のキーワード: transferase, heme biosynthesis, 5-aminolevulinic acid, pyridoxal 5-phosphate
• 由来する生物種: Saccharomyces cerevisiae (baker's yeast)
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 105901.41

構造登録者

Tran, J.U.,Brown, B.L. (登録日: 2022-09-15, 公開日: 2023-03-15, 最終更新日: 2023-10-25)

主引用文献

Tran, J.U.,Brown, B.L.
The yeast ALA synthase C-terminus positively controls enzyme structure and function.
Protein Sci., 32:e4600-e4600, 2023

PubMed Abstract: 5-Aminolevulinic acid synthase (ALAS) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the first and rate-limiting step of heme biosynthesis in α-proteobacteria and several non-plant eukaryotes. All ALAS homologs contain a highly conserved catalytic core, but eukaryotes also have a unique C-terminal extension that plays a role in enzyme regulation. Several mutations in this region are implicated in multiple blood disorders in humans. In Saccharomyces cerevisiae ALAS (Hem1), the C-terminal extension wraps around the homodimer core to contact conserved ALAS motifs proximal to the opposite active site. To determine the importance of these Hem1 C-terminal interactions, we determined the crystal structure of S. cerevisiae Hem1 lacking the terminal 14 amino acids (Hem1 ΔCT). With truncation of the C-terminal extension, we show structurally and biochemically that multiple catalytic motifs become flexible, including an antiparallel β-sheet important to Fold-Type I PLP-dependent enzymes. The changes in protein conformation result in an altered cofactor microenvironment, decreased enzyme activity and catalytic efficiency, and ablation of subunit cooperativity. These findings suggest that the eukaryotic ALAS C-terminus has a homolog-specific role in mediating heme biosynthesis, indicating a mechanism for autoregulation that can be exploited to allosterically modulate heme biosynthesis in different organisms.

PubMed: 36807942
DOI: 10.1002/pro.4600

実験手法

X-RAY DIFFRACTION (2.1 Å)