NMR structure and dynamics of inhibitory repeat domain variant 12, a plant protease inhibitor from Capsicum annuum, and its structural relationship to other plant protease inhibitors

Abstract

Although several plant protease inhibitors have been structurally characterized using X-ray crystallography, very few have been studied using NMR techniques. Here, we report an NMR study of the solution structure and dynamics of an inhibitory repeat domain (IRD) variant 12 from the wound-inducible Pin-II type proteinase inhibitor from Capsicum annuum. IRD variant 12 (IRD12) showed strong anti-metabolic activity against the Lepidopteran insect pest, Helicoverpa armigera. The NMR-derived three-dimensional structure of IRD12 reveals a three-stranded anti-parallel β-sheet rigidly held together by four disulfide bridges and shows structural homology with known IRDs. It is interesting to note that the IRD12 structure containing ∼75% unstructured part still shows substantial amount of rigidity of N–H bond vectors with respect to its molecular motion.

Communicated by Ramaswamy H. Sarma

Keywords:

• Protease inhibitors (PIs)
• Bt transgenic
• inhibitory repeating domains
• NMR structure
• Helicoverpa armigera
• Capsicum annuum

Acknowledgements

We acknowledge financial support from the Indian agencies (Indo-Australian joint project DST/INT/AUS/P-63/2015) to K.V.R.C. and UGC-faculty recharge program and DST-ECRA/2017/000124 award to R.P.B., Australia-India Strategic Research Fund (AISRF-1277949-197), Department of Biotechnology (DBT), Council of Scientific and Industrial Research (CSIR), Tata Institute of Fundamental Research (TIFR) and the Australian National Health & Medical Research Council (Principal Research Fellowship APP1136889 to G.F.K.). We also acknowledge the National Facility of High-Field NMR, supported by Department of Science and Technology (DST), Department of Biotechnology (DBT), Council of Scientific and Industrial Research (CSIR) and Tata Institute of Fundamental Research (TIFR), Mumbai.

Disclosure statement

No potential conflict of interest was reported by the authors.