Table 1.

Deduced functions of ORFs in the avermection biosynthetic gene cluster

Polypeptide	Amino acids, no.	Proposed function or sequence similarities detected
AVES 1	3,953	PKS
Loading domain			AT(MB)			ACP
Module 1		KS	AT(P)		KR	ACP
Module 2		KS	AT(A)	DH	KR	ACP
AVES 2	6,239	PKS
Module 3		KS	AT(A)			ACP
Module 4		KS	AT(A)		KR	ACP
Module 5		KS	AT(A)		KR	ACP
Module 6		KS	AT(P)	DH	KR	ACP
AVES 3	5,532	PKS
Module 7		KS	AT(P)	DH*	KR	ACP
Module 8		KS	AT(A)	DH	KR	ACP
Module 9		KS	AT(P)	DH	KR	ACP
AVES 4	4,881	PKS
Module 10		KS	AT(A)		KR*	ACP
Module 11		KS	AT(P)			ACP
Module 12		KS	AT(A)	DH	KR	ACP	TE
ORF 1	238	Reductase ?†
AveBI	412	Glycosyl transferase
AveBII	355	dTDP-glucose 4,6-dehydratase
AveBIII	299	α-d-Glucose-1-phosphate thymidylyltransferase
AveBIV	343	dTDP-4-keto-6-deoxy-l-hexose 4-reductase
AveBV	225	dTDP-4-keto-6-deoxyhexose 3,5-epimerase
AveBVI	469	dTDP-4-keto-6-deoxy-l-hexose 2,3-dehydratase
AveBVII	257	dTDP-6-deoxy-l-hexose 3-O-methyltransferase
AveBVIII	347	dTDP-4-keto-6-deoxy-l-hexose 2,3-reductase
AveC	347	?
AveD	283	C5-O-methyltransferase
AveE	456	Cytochrome P450 hydroxylase
AveF	302	C5-ketoreductase
AveR	949	Positive 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.