Plant intracellular nucleotide-binding, leucine-rich repeat immune receptors (NLRs) recognise pathogen effectors to trigger plant immunity. However, plants are still under constant threat as pathogens often overcome plant immunity due to rapid evolution. Engineering of plant NLR immune receptors has been demonstrated to be a promising strategy for generating receptors with expanded or new-to-nature pathogen recognition profiles. Here we show that the recognition specificity of the stem rust (Puccinia graminisf. sp.tritici) AvrSr50 and AvrSr33 effector can be transferred between the wheat NLR immune receptor Sr50 and its homologous NLR Sr33 by swapping LRR domains. We further narrowed down the critical region for AvrSr50 recognition to 3 LRR units on Sr50, which are also responsible for the autoactivity of Sr50. By combining AvrSr50 structure and recognition information, we predicted the Sr50-AvrSr50 interaction structural interface, in which the key residue Q121 required for AvrSr50 recognition is placed within a pocket made by variant amino acids in the 3 LRR units. By introducing mutations to these variant amino acids, we found mutations on two adjacent amino acids abolish the autoactivity of Sr50 but keep the recognition of AvrSr50. Furthermore, mutations of these two amino acids recover recognition of the non-recognised virulence alleles avrSr50-B6 and D, in which the key residue Q121 was substituted to K and L. Our findings suggest we can accurately predict structural models for NLR-Avr protein interactions, enabling NLR engineering to expand recognition profiles.