gamma-Conglutin, the Lupinus albus XEGIP-like protein, whose expression is elicited by chitosan, lacks of the typical inhibitory activity against GH12 endo-glucanases.
gamma-Conglutin, a glycoprotein from Lupinus albus seed, has been characterized at molecular level but its physiological function is still unknown. gamma-Conglutin shares a high structural similarity with xyloglucan-specific endo-beta-1,4-glucanase inhibitor proteins (XEGIPs) and Triticum aestivum xylanase inhibitor (TAXI-I), which act specifically against fungal glycosyl hydrolase belonging to families 12 and 11, respectively. To assess the possible involvement of gamma-conglutin in plant defense, germinating lupin seeds were incubated with chitosan. The relative quantification of gamma-conglutin mRNA extracted from cotyledons was then carried out by RT-qPCR and indicated that chitosan strongly elicited the expression of gamma-conglutin. Moreover, biochemical trials aimed to test the inhibitory capacity of the protein have been also carried out. gamma-Conglutin failed to inhibit representative fungal endo-glucanases and other cell wall-degrading enzymes. To explain the lack of inhibitory capacity we investigated the possible structural differences between gamma-conglutin and XEGIPs and TAXI-I, including the construction of a predictive 3D model of the protein. Bioinformatic analysis suggests that the lack of inhibitory activity of gamma-conglutin can be attributed to sequence differences in the inhibitor interaction domains, and in particular to a sequence deletion in one of the functional loops.
Scarafoni
Alessio
A
Dipartimento di Scienze Molecolari Agroalimentari, Università degli Studi di Milano, via G. Celoria 2, 20133 Milano, Italy. alessio.scarafoni@unimi.it
Ronchi
Alessandro
A
Duranti
Marcello
M
D000595:Amino Acid Sequence; D048271:Chitosan / Q000494:pharmacology; D003198:Computer Simulation; D018548:Cotyledon; D043364:Endo-1,4-beta Xylanases / Q000037:antagonists & inhibitors*; D005658:Fungi / Q000737:chemistry / Q000201:enzymology*; D015870:Gene Expression; D018525:Germination; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors*; D031297:Lupinus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds; D017384:Sequence Deletion; D017385:Sequence Homology; D014908:Triticum / Q000235:genetics / Q000378:metabolism
D006023:Glycoproteins; D010940:Plant Proteins; D012333:RNA, Messenger; D048271:Chitosan; D006026:Glycoside Hydrolases; D043364:Endo-1,4-beta Xylanases