Table 1

Deduced functions of ORFs in the avermection biosynthetic gene cluster

PolypeptideAmino acids, no.Proposed function or sequence similarities detected
AVES 13,953PKS
 Loading domainAT(MB) ACP
 Module 1KSAT(P)KRACP
 Module 2KSAT(A)DHKRACP
AVES 26,239PKS
 Module 3KSAT(A)ACP
 Module 4KSAT(A)KRACP
 Module 5KSAT(A)KRACP
 Module 6KSAT(P)DHKRACP
AVES 35,532PKS
 Module 7KSAT(P)DH*KRACP
 Module 8KSAT(A)DHKRACP
 Module 9KSAT(P)DHKRACP
AVES 44,881PKS
 Module 10KSAT(A)KR*ACP
 Module 11KSAT(P)ACP
 Module 12KSAT(A)DHKRACPTE
ORF 1238Reductase ?
AveBI412Glycosyl transferase
AveBII355dTDP-glucose 4,6-dehydratase
AveBIII299α-d-Glucose-1-phosphate thymidylyltransferase
AveBIV343dTDP-4-keto-6-deoxy-l-hexose 4-reductase
AveBV225dTDP-4-keto-6-deoxyhexose 3,5-epimerase
AveBVI469dTDP-4-keto-6-deoxy-l-hexose 2,3-dehydratase
AveBVII257dTDP-6-deoxy-l-hexose 3-O-methyltransferase
AveBVIII347dTDP-4-keto-6-deoxy-l-hexose 2,3-reductase
AveC347?
AveD283C5-O-methyltransferase
AveE456Cytochrome P450 hydroxylase
AveF302C5-ketoreductase
AveR949Positive regulator
  • Abbreviations are the same as in Fig. 2. AT(MB), acyltransferase incorporating a 2-methylbutyrate or isobutyrate extender unit; AT(A), acyltransferase incorporating an acetate extender unit; AT(P), acyltransferase incorporating a propionate extender unit. Partial or low-level sequence similarities are indicated by question marks. 

  • * Enzyme activity is possible nonfunctional (see text). 

  • The gene product is not involved in avermectin biosynthesis.