Abstract: To determine the amino acid region on SRK responsible for binding THL1 and their interaction manner，according to distribution of functional domains on SRKE1,two truncated form of SRKE1 prokaryotic expression plasmids pGEX-SRKE1A and pGEX-SRKE1B were constructed，and the recombinant protein were expressed in E. coli（BL21）. SRKE1A and SRKE1B were incubated with THL1 respectively，their interaction were analyzed in vitro. The result showed that SRKE1A and SRKE1B could interact with THL1，and their interaction did not depend on SRK kinase activity. Through alignment of SRKs from ClassⅠand ClassⅡ，the result showed that the conserved cysteine sites were different between the two Class SRKs，which suggests that self-incompatibility difference between two Class SRK probably has relation to the conserved Cys.

Key words: Brassica oleracea, S-locus receptor kinase, thioredoxin-h-like protein 1, interaction