Homo sapiens

    Autophagocytosis associated protein C-terminal (Autophagy_C) domain (1) is likely to be a distinct binding region for the stability of the autophagosome complex (2). It carries a highly characteristic conserved FLKF sequence motif.

1. http://pfam.xfam.org/family/PF10381

2. Noda T, Fujita N, Yoshimori T (May 2008). The Ubi brothers reunited. Autophagy., 4 (4): 540–1. PMID: 18398292

    E2/Other family is a collection of unconventional E2s which does not contain the UBC domain. E2s for ubiquitin-like (UBL) conjugates involved in autophagy such as Atg8/12 conjugates are included (1). UFC1, the E2 for Ufm1, is also in this family (2).

1. van Wijk, S.J. and Timmers, H.T. (2010) The family of ubiquitin-conjugating enzymes (E2s): deciding between life and death of proteins. FASEB J., 24, 981-993.PMID: 19940261

2. Komatsu, M., Chiba, T., Tatsumi, K., Iemura, S., Tanida, I., Okazaki, N., Ueno, T., Kominami, E., Natsume, T. and Tanaka, K. (2004). A novel protein-conjugating system for Ufm1, a ubiquitin-fold modifier. EMBO J., 23, 1977-1986.PMID: 15071506

    UBC is the abbreviation of ubiquitin-conjugating. Most ubiquitin-conjugating enzymes (E2s) possess a core UBC domain, which contains the catalytic cysteine residue and interacts with E1s. E2 catalyzes the second step in the ubiquitination reaction, which targets a protein for degradation via the proteasome (1). Besides ubiquitination, E2s catalyzes ubiquitin-like modification. Once conjugated to ubiquitin or ubiquitin-like by E1 enzyme, the E2 enzyme binds one of several ubiquitin ligases or E3s via a structurally conserved binding region. Finally, the target protein substrate gets more and more ubiquitin molecules or ubiquitin-like molecules from E2 by E3.

1. http://en.wikipedia.org/wiki/Ubiquitin-conjugating_enzyme

    UEV represents the Ubiquitin E2 variant (UEV) proteins which have a UBC domain but lack the active-site cysteine residue (1).

1. Ye, Y. and Rape, M. (2009). Building ubiquitin chains: E2 enzymes at work. Nat. Rev. Mol. Cell Biol., 10, 755-764. PMID: 19851334