Table 1.

Features and putative functions of ast cluster genes

Locus tag	Gene name	No. of Introns	No. of amino acids	Conserved domain(s)/proposed function	Possible role in astin biosynthesis
VA03HOR0624_x10098	astL	1	353	Unknown	Unknown
VA03HOR0624_x10099	astM	5	650	Bromodomain, chromatin-associated protein	Transcriptional regulation
VA03HOR0624_x10100	astN	2	5,584	NRPS	Astin synthetase
VA03HOR0624_x10101	astO	0	1,530	ABC-type exporter	Efflux/intercompartmental transport
VA03HOR0624_x10102	astP	3	682	Aminomutase	Biosynthesis of βPhe*
VA03HOR0624_x10103	astQ	1	79	Unknown	Unknown
VA03HOR0624_x10104	astR	1	476	Aminotransferase	Biosynthesis of 2Abu†
VA03HOR0624_x10105	astS	3	320	DUF3328‡	Unknown
VA03HOR0624_x10106	astT	0	483	Transporter (major facilitator superfamily)	Efflux/intercompartmental transport
VA03HOR0624_x10107	astU	4	373	DUF3328‡	Unknown
VA03HOR0624_x10108	astV	1	227	DUF3328‡	Unknown
VA03HOR0624_x10109	astW	2	1,338	ABC-type exporter	Efflux/intercompartmental transport
VA03HOR0624_x10110	astX	1	691	Transcriptional regulator (ICP4 domain); signal transduction (tetratricopeptide repeat)	Transcriptional regulation

^*Detailed amino acid sequence analysis of AstP reveals characteristic features of phenylalanine aminomutases according to Heberling et al. (76) (see SI Appendix, Fig. S14 for more information).

^†The building block 2Abu can be generated from l-threonine via α-ketobutyric acid by the concerted action of a threonine dehydratase and an aminotransferase (77). The cluster-encoded aminotransferase AstR is proposed to catalyze the second step in this reaction.

^‡DUF3328, domain of unknown function 3328. Proteins containing DUF3328 have recently been shown to be involved in fungal NP biosynthesis (78).