Electron microscopy analysis of mammalian phosphofructokinase reveals an unusual 3-dimensional structure with significant implications for enzyme function.
Phosphofructokinase is a sophisticated allosteric enzyme that is fundamental for the control of glycolysis. The structure of the bacterial enzyme is well characterized. However, little is known about the structural organization of the more complex enzyme from mammals. We have obtained the structure of human muscle phosphofructokinase in the presence of fructose 6-phosphate at a resolution of 1.8 nm by electron microscopy (EM). Particles of the tetrameric enzyme corresponded to an elongated molecule (14.5 × 9 nm) arranged into 2 dimeric subdomains. Image analysis and 3-dimensional reconstruction showed the presence of a prominent channel in one of the dimers but not in the opposite one, revealing that they are in greatly different conformations. Fitting of bacterial structures into the EM model suggested disruption of the fructose 6-phosphate catalytic and the fructose 2,6-bisphophate allosteric sites in the cavity-containing dimer. Therefore, the reported structure might have major implications for the function of mammalian phosphofructokinase.
Arechaga
Ignacio
I
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.
Martínez-Costa
Oscar H
OH
Ferreras
Cristina
C
Carrascosa
José L
JL
Aragón
Juan J
JJ
D006801:Humans; D008855:Microscopy, Electron, Scanning; D008958:Models, Molecular; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism*; D025203:Phosphofructokinase-1, Muscle Type / Q000737:chemistry / Q000378:metabolism; D025221:Phosphofructokinases / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D009124:Muscle Proteins; D025221:Phosphofructokinases; D025203:Phosphofructokinase-1, Muscle Type