Modification and adaptor antibodies are bought to show that a pathway ran, and pathways are read as changes in state rather than in amount: a modified pool appears, an adaptor relocates, a scaffold is degraded. The buffers protect the modification, the fractionation finds the complex, and the positive control is a treatment rather than a cell line.
A ddb1 antibody and an rnf43 antibody on ligase machinery
Both are parts of ubiquitin ligase complexes rather than enzymes read on their own. The damage-specific adaptor is abundant and constitutive, which makes it a useful anchor when a substrate receptor is being pulled down, and a poor readout of pathway activity. The membrane ligase is read for its effect on Wnt receptor levels, so the informative experiment measures its substrate rather than the ligase, and a knockout line is what settles the antibody's specificity in a family with close relatives.
A fadd antibody and an irak4 antibody on death and innate adaptors
Adaptors work by being recruited, so a total blot changes little while the biology changes completely, and the informative experiments are immunoprecipitation after stimulation, a fractionation, or imaging of the complex. That means a gentle lysis buffer, a stimulation with a documented agonist and time, and a reciprocal pull down where an interaction is claimed. Phospho clones exist for the kinase and are read with a total antibody on the same membrane.
A beclin-1 antibody and an lc3b antibody on autophagy
The lipidated form of the autophagy marker migrates faster than the unmodified one, so the readout is a ratio on a gel that resolves the two, and it rises both when autophagy runs and when the lysosome is blocked, which is why a flux design with and without an inhibitor is the measurement rather than a control. The initiation scaffold is read for its interactions and its cleavage rather than its amount, and an inhibitor arm plus a starvation arm belong in the first experiment.
A rad50 antibody and an apc antibody on repair and destruction complexes
The repair complex subunit is read as foci at breaks, which makes imaging after a documented insult the informative experiment, with a nuclear extract for the blot. The tumour suppressor is a very large scaffold, so it needs a gel and a transfer that will carry it, and a truncating mutation in a cell line produces a shorter product that a clone raised beyond the truncation cannot see, which is the specificity question that matters for it.
Modified pools, and the buffers that preserve them
Small modifier conjugates are removed by proteases and isopeptidases within seconds of lysis, so the buffer carries the right inhibitors, N-ethylmaleimide for the small modifier and ubiquitin aldehyde or a deubiquitinase inhibitor where ubiquitin is the readout, and the sample is denatured quickly rather than kept gently on ice. A high salt or denaturing lysis is often better here than the gentle buffer a complex needs, which is why one experiment cannot answer both questions.
Free modifier against conjugates
An antibody against a small modifier detects the free protein and everything conjugated to anything, so a blot is a ladder rather than a band and the interesting signal is a shift in the pattern. Where a specific substrate is the question, the experiment is an immunoprecipitation of the substrate followed by a blot for the modifier, or the reverse, with a denaturing wash so co-precipitating partners do not confuse the result. Overexpressing tagged modifier makes it easier and changes the biology.
Flux and recruitment designs
Two designs cover most of this class. Flux: the same treatment with and without a lysosomal or proteasomal inhibitor, read as the difference between the pairs. Recruitment: stimulate, fractionate or immunoprecipitate, and show the adaptor arriving where it was not before. Both need a time course rather than a single point, because adaptor recruitment peaks in minutes and degradation in hours, and a single time point is how two laboratories reach opposite conclusions.
What to ask for on this class
Ask what the vendor's figure treated the cells with and for how long, whether the clone is qualified for immunoprecipitation as well as blotting, and what the immunogen is, since a modifier's paralogues and an adaptor's family relatives share epitopes. Ask for knockout material where it exists. And ask which gel percentage and transfer their figure used for the very large proteins in this set, because a scaffold that never leaves the gel reads as an absent protein.
Questions people ask about sumo antibody
Why is an autophagy marker's rise ambiguous?
Because it is degraded by the pathway it marks. Run the treatment with and without a lysosomal inhibitor and read the difference between pairs.
What has to be in the lysis buffer?
Inhibitors of the proteases that remove the modification: N-ethylmaleimide for small modifiers, a deubiquitinase inhibitor where ubiquitin is the readout, with quick denaturation.
Why does a total adaptor blot show nothing?
Because adaptors work by recruitment rather than by abundance. Fractionate or immunoprecipitate after a timed stimulation instead.