Selecting an appropriate method for expressing S locus F-box-S2 recombinant protein.

•Understanding the molecular basis of self-incompatibility (SI) is essential for commercial production of fruit crops such as Apple.•To investigate the molecular interactions in self-incompatibility locus (Slocus), the knowledge of tertiary structures of both male (i.e. S-locus F-box) and female (i.e. SRNase) proteins are necessary.•The tertiary structure of male determinant (S locus F-box, SLF/SFB) remains unresolved, which could mainly be due to difficulties associated with its expression in the recombinant expression systems.•This study demonstrates an approach for efficient expression of S locus F-box recombinant proteins for future functional and structural studies.