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Structure-function relationship in spinach ferredoxin-NADP+ reductase as studied by limited proteolysis
G Gadda1, A Aliverti, S Ronchi
1Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italy.
The Journal of Biological Chemistry
|July 15, 1990
Summary
Limited proteolysis of ferredoxin-NADP+ reductase revealed two protease-susceptible regions. Ligand protection suggests these sites are crucial for ferredoxin and NADP+ binding, impacting enzyme activity.
Area of Science:
- Biochemistry
- Enzymology
- Protein Chemistry
Background:
- Ferredoxin-NADP+ reductase (FNR) is a key enzyme in electron transport.
- Understanding FNR's structure-function relationship is vital for its catalytic mechanisms.
Purpose of the Study:
- To investigate the structural regions of FNR susceptible to proteolysis.
- To determine the role of specific FNR regions in its enzymatic activities and ligand binding.
Main Methods:
- Limited proteolysis of purified FNR using various proteases.
- Assays for diaphorase and ferredoxin-dependent activities.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for proteolytic pattern analysis.
Main Results:
- Two protease-susceptible regions identified: N-terminal (up to Lys35) and sequence segment 235-250.
- Cleavage at the N-terminus (up to Thr36) yielded a truncated FNR with full diaphorase activity but lost ferredoxin-dependent activity.
- Cleavage at the 235-250 segment resulted in a nicked FNR devoid of both activities.
Conclusions:
- The N-terminal region (residues 23-35) is involved in ferredoxin binding.
- The 235-250 polypeptide segment is part of the NADP+ binding site.
- Ligand protection of these regions highlights their importance in FNR's catalytic function.