Combined experimental and theoretical study of long-range interactions modulating dimerization and activity of yeast geranylgeranyl diphosphate synthase.
We present here how two amino acid residues in the first helix distal from the main dimer interface modulate the dimerization and activity of a geranylgeranyl diphosphate synthase (GGPPs). The enzyme catalyzes condensation of farnesyl diphosphate and isopentenyl diphosphate to generate a C(20) product as a precursor for chlorophylls, carotenoids, and geranylgeranylated proteins. The 3D structure of GGPPs from Saccharomyces cerevisiae reveals an unique positioning of the N-terminal helix A, which protrudes into the other subunit and stabilizes dimerization, although it is far from the main dimer interface. Through a series of mutants that were characterized by analytic ultracentrifugation (AUC), the replacement of L8 and I9 at this helix with Gly was found sufficient to disrupt the dimer into a monomer, leading to at least 10(3)-fold reduction in activity. Molecular dynamics simulations and free energy decomposition analyses revealed the possible effects of the mutations on the protein structures and several critical interactions for maintaining dimerization. Further site-directed mutagenesis and AUC studies elucidated the molecular mechanism for modulating dimerization and activity by long-range interactions.
Lo
Chia-Hsiang
CH
Institute of Biochemical Sciences, National Taiwan University, Taipei.
Chang
Ying-Hsuan
YH
Wright
Jon D
JD
Chen
Shih-Hsun
SH
Kan
Daphne
D
Lim
Carmay
C
Liang
Po-Huang
PH
D003198:Computer Simulation; D051231:Farnesyltranstransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D016296:Mutagenesis; D011487:Protein Conformation; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013816:Thermodynamics
D051231:Farnesyltranstransferase