Table 2.

Phenotypes of rad6ΔC, ubc1ΔC, and UBC4a

Group and substitution typeE2Substitution(s)Viability at 30°C (ubc4Δ ubc5Δ)b% Viability in canavanine (ubc4Δubc5Δ)c% Viability under UV light (rad6Δ)dThiolester formatione
 1rad6ΔCNone (parental)+98100
 2ubc1ΔCNone (parental)+++++22100
 3UBC4None (parental)++++++33NDf
 5rad6ΔCN65F+++ 471ND
 9rad6ΔCN123V+ 6ND
 12rad6ΔCN65F, Y82N++++1347ND
 13rad6ΔCS120D, N123V+84
 18UBC4F63N, N80Y, D118S, V121N+++++25ND
 19rad6ΔC1–10 Residues 1–10 from Ubc4+70ND
 20rad6ΔCCdc34 Residues 101–112 from Cdc34NDNDND
 22ubc41–8 Residues 1–8 from Rad6++++++42ND
 23ubc41–50 Residues 1–52 from Rad6++++ND
 28ubc1ΔCE125A, H129A, L131A, R132A, E135A+++++14ND122
  • a Plasmids are numbered and grouped as in Table I. Plasmids with phenotypes that do not differ significantly from the parental control were excluded (4, 7, 10, 11, 14 to 16, 28, and 30). Growth and canavanine sensitivity were measured in theubc4Δ ubc5Δ-null strain (MHY508).

  • b Growth was scored relative to the colony size of the null strain (+) and the null strain carrying the UBC4positive control plasmid (++++++).

  • c Canavanine sensitivity was measured as the percentage of colonies formed on canavanine-containing plates relative to colony formation on plates without canavanine. A minus sign denotes a level of viability of less than 0.1%.

  • d UV sensitivity was measured inrad6Δ-null strain KMY20. The percentage of viable cells following irradiation was calculated as the number of colonies formed relative to the number formed by an unirradiated control. A minus sign denotes a level of survival of less than 0.1%.

  • e Ubiquitin thiolester formation was measured in vitro by using purified components as described in Materials and Methods. Values are expressed as the percentage of thiol ester formed relative to that formed by the appropriate parental E2.

  • f ND, not determined.