Table 1.

Strains, plasmids and primers used in this study

Strain/plasmid/primer	Description	Source
Strains
E. coli Top 10	A strain for high-efficiency cloning and plasmid propagation	TransGen Biotech, China
P. pastoris GS115	A methylotrophic yeast having a mutation in the histidinol dehydrogenase gene (his4)	TransGen Biotech, China
Plasmids
pGEM-T	A vector system for cloning of PCR products	Invitrogen, USA
pPIC9 K	A P. pastoris expression vector carrying kanamycin resistance gene	Invitrogen, USA
Primersa
P1	F: 5′-TTCCTAGGATGTCAGAAGTTTCCAAATG-3′	Sangon Biotech, China
	R: 5′-TAGCGGCCGCGTGTGACATCATACGACTAA-3′
P2	F: 5′-TTCCTAGGATGTTTCGCTCGGGT-3′	Sangon Biotech, China
	R: 5′-ATGCGGCCGCAACATATTTATAAAACTAAC T-3′

^aThe restriction sites are underlined.