The FGFR1 kinase is bound to the N-SH2 domain primarily through charged amino acids. Arginine residue (R609) on the N-SH2 domain forms a salt bridge to aspartate 755 (D755) on the FGFR1 domain. The acid base pair located in the middle of the interface are nearly parallel to each other, indicating a highly favorable interaction. N-SH2 domain makes an additional polar contact through water-mediated interaction that takes place between the N-SH2 domain and FGFR1 kinase. Interestingly, the arginine residue 609 (R609) on the FGFR1 kinase also forms a salt bridge to the aspartate residue (D594) on the N-SH2 domain. The acid-base pair interacts with each other carry out redox reaction to stabilize the complex.