Interesting question. May be its a beta isoform (SDHB) and there could be an alpha isoform (SDHA) which does the job (TCA). Check your cells for the presence of mitochondria by JC1 staining (in case if mitophagy is the cause behind such results).

I have generally found these cocktails to be really good, however you can occasionally lose a band for a particular complex if you boil the samples. This happened to me once with complex IV but I was able to get a complex IV band with a different antibody.

Hi Amy!

Not a fully functional TCA cycle is required for the synthesis of aminoacids. For example, alpha-ketoglutarate, the precursor of glutamate, can be synthetized by a partial TCA cycle in the presence of excessive concentrations of acetyl-CoA, which suppresses piruvate dehydrogenase and activates piruvate carboxylase, which synthesizes oxaloacetate using piruvate as substrate. This provides enough oxaloacetate for its reaction with acetyl-CoA to provide citrate for its sucesive convertion to isocitrate and then, to alpha-ketoglutarate, yielding a functional, truncated, TCA cycle able to synthesize glutamate. There are other examples of amino acids that can be synthesized with a truncated TCA cycle due to the activity of anaplerotic pathways.

I hope my response may be helpful to you

Best wishes

Christian

Good Question

Please check the thermal status of the reaction

and check the viability after each step

On the other hand, the other important thing to be considered is that complex II is not codified by mtDNA. Thus, as stated in the other responses, there would be some technical issue with your assay.

nothing to add now, Christian is perfectly right - still strange that you dont see CxII, guess its really lysis conditions etc., we do see it in 143B and Hela rho zero. Keep going