Escherichia coli pyruvate dehydrogenase complex: particle masses of the complex and component enzymes measured by scanning transmission electron microscopy

Publisher Website
Google Scholar
Abstract
Particle masses of the Escherichia coli pyruvate dehydrogenase (PDH) complex and its component enzymes were measured by scanning transmission electron microsopy (STEM). The particle mass of PDH complex measured by STEM is 5.28 x 106 with a (SD 0.40 .times. 106). The masses of the component enzymes together with their SD are (2.06 .+-. 0.26) .times. 105 for the dimeric pyruvate dehydrogenase (E1) (1.15 .+-. 0.17) .times. 105 for dimeric dihydrolipoyl dehydrogenase (E3) and (2.20 .+-. 0.17) .times. 106 for dihydrolipoyl transacetylase (E2), the 24-subunit core enzyme. The latter value corresponds to a subunit MW of (9.17 .+-. 0.71) .times. 104 for E2. The subunit MW measured by polyacrylamide gel electrophoresis in sodium dodecyl sulfate is 8.6 .times. 104. STEM measurements on PDH complex incubated with excess E3 or E2 failed to detect any additional binding of E3 but showed that the complex would bind additional E1 under forcing conditions (high concentrations with glutaraldehyde). The additional E1 subunits were bound too weakly to represent binding sites in an isolated or isolable complex. The mass measurements by STEM are consistent with the subunit composition 24:24:12 when interpreted in the light of the flavin content of the complex and assuming 24 subunits in the core enzyme (E2).

This publication has 23 references indexed in Scilit: