What is non-canonical polyubiquitination?

[IRyanI]

I'm reading a research article and the sentence is, "TRAF2 is an E3 ligase that binds to Ubc13, resulting in non-canonical polyubiquitination of substrates involving lysine 63 rather than the canonical lysine 48 linking site."

What's it mean to be a non-canonical lysine and how does it differ in terms of structure and role from a canonical lysine? Am I even asking the right question here?

Thanks!

[JackBean]

I think that non-canonical here means something like non-standard or non-usual

[JackBean]

i.e. usually is the ubiquitin bound to K48, while in your case it is K63

[IRyanI]

Sometimes the answer is more simple than you would assume. Thanks for the response JackBean.