A novel homodimeric lectin from Astragalus mongholicus with antifungal activity.
A novel lectin (AMML) was isolated from a Chinese herb, i.e., the roots of Astragalus mongholicus, using a combination of ammonium sulfate fraction and ion exchange chromatographies. The molecular mass of intact AMML was determined to be 66,396 Da by MALDI-TOF mass spectrometry and 61.8 kDa by gel filtration, respectively. AMML was a dimeric protein composed of two identical subunits each with a molecular mass of 29.6 kDa. The lectin was a glycoprotein with a neutral carbohydrate content of 19.6%. The purified lectin hemagglutinated both rabbit and human erythrocytes, and showed preference for blood types O (native) and AB (trypsin-treated). Among various carbohydrates tested, the lectin was best inhibited by D-galactose and its derivatives with pronounced preference for lactose (3.13 mM). N-terminal amino acid sequence of AMML was determined as ESGINLQGDATLANN. The optimal pH range for lectin activity was between pH 4.5 and 7.5, and the lectin was active up to 65 degrees C. It also exerted antifungal activity against Botrytis cincerea, Fusarium oxysporum, Colletorichum sp., and Drechslera turcia but not against Rhizoctonia solani and Mycosphaerella arachidicola.
Yan
Qiaojuan
Q
Bioresource Utilization Laboratory, Engineering College, China Agricultural University, Beijing 100083, China. yanqj@cau.edu.cn
Jiang
Zhengqiang
Z
Yang
Shaoqing
S
Deng
Wei
W
Han
Lujia
L
D000595:Amino Acid Sequence; D000645:Ammonium Sulfate / Q000737:chemistry; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D027883:Astragalus Plant / Q000737:chemistry*; D001789:Blood Group Antigens / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D019281:Dimerization; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism; D005658:Fungi / Q000187:drug effects* / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006384:Hemagglutination; D006863:Hydrogen-Ion Concentration; D037102:Lectins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011817:Rabbits; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000935:Antifungal Agents; D001789:Blood Group Antigens; D006023:Glycoproteins; D037102:Lectins; D000645:Ammonium Sulfate; D005690:Galactose