Identification and cloning of a trypsin inhibitor from skin secretions of Chinese red-belly toad Bombina maxima

A novel trypsin inhibitor was identified and purified from skin secretions of Chinese red-belly toad Bombina maxima. The partial N-terminal 29 amino acid residues of the peptide, named BMTI, were determined by automated Edman degradation. This allowed the cloning of a full-length cDNA encoding BMTI from a cDNA library prepared from the toad skin. The deduced complete amino acid sequence of BMTI indicates that mature BMTI is composed of 60 amino acids. A FASTA search in the databanks revealed that BMTI exhibits 81.7% sequence identity with BSTI, a trypsin/thrombin inhibitor from European toad Bombina bombina skin secretions. Sequence differences between BMTI and BSTI were due to 11 substitutions at positions 2, 9, 25, 27, 36-37, 39, 41-42, 50 and 56. BMTI potently inhibited trypsin with a K-i value of 0.06 muM, similar to that of BSTI. However, unlike BSTI, which also inhibited thrombin with a K-i value of 1 muM, no inhibitory effect of BMTI on thrombin was observed under the assay conditions. (C) 2002 Elsevier Science Inc. All rights reserved.

Frog albumin is expressed in skin and characterized as a novel potent trypsin inhibitor

A novel potent trypsin inhibitor was purified and characterized from frog Bombina maxima skin. A full-length cDNA encoding the protein was obtained from a cDNA library constructed from the skin. Sequence analysis established that the protein actually comprises three conserved albumin domains. B. maxima serum albumin was subsequently purified, and its coding cDNA was further obtained by PCR-based cloning from the frog liver. Only two amino acid variations were found in the albumin sequences from the skin and the serum. However, the skin protein is distinct from the serum protein by binding of a haem b (0.95 mol/mol protein). Different from bovine serum albumin, B. maxima albumin potently inhibited trypsin. It bound tightly with trypsin in a 1: 1 molar ratio. The equilibrium dissociation constants (K-D) obtained for the skin and the serum proteins were 1.92 x 10(-9) M and 1.55 x 10(-9) M, respectively. B. maxima albumin formed a noncovalent complex with trypsin through an exposed loop formed by a disulfide bond (Cys(53)-Cys(62)), which comprises the scissile bond Arg(58)(P-1)-His(59)(P-1'). No inhibitory effects on thrombin, chymotrypsin, elastase, and subtilisin were observed under the assay conditions. Immunohistochemical study showed that B. maxima albumin is widely distributed around the membranes of epithelial layer cells and within the stratum spongiosum of dermis in the skin, suggesting that it plays important roles in skin physiological functions, such as water economy, metabolite exchange, and osmoregulation.

A small trypsin inhibitor from the frog of Odorrana grahami

A novel peptide inhibitor (OGTI) of serine protease with a molecular weight of 1949.8, was purified from the skin secretion of the frog, Odorrana grahami. Of the tested serine proteases, OGTI only inhibited the hydrolysis activity of trypsin on synthetic chromogenic substrate. This precursor deduced from the cDNA sequence is composed of 70 amino acid residues. The mature OGTI contains 17 amino acid residues including a six-residue loop disulfided by two half-cysteines (AVNIPFKVHFRCKAAFC). In addition to its unique six-residue loop, the overall structure and precursor of OGTI are different from those of other serine protease inhibitors. It is also one of the smallest serine protease inhibitors ever found. (C) 2008 Elsevier Masson SAS. All rights reserved.

Isolation and preliminary characterization of a 22-kDa protein with trypsin inhibitory activity from toad Bufo andrewsi skin

A novel trypsin inhibitor termed BATI was purified to homogeneity from the skin extracts of toad Bufo andrewsi by successive ion-exchange, gel-filtration and reverse-phase chromatography. BATI is basic single chain glycoprotein, with apparent molecular weight of 22 kDa in SDS-PAGE. BATI is a thermal stable competitive inhibitor and effectively inhibits trypsin's catalytic activity on peptide substrate with the inhibitor constant (K-i) value of 14 nM and shows no inhibitory effect on chymotrypsin, thrombin and elastase. The N-terminal sequence of BATI is EKDSITD, which shows no similarity with other known trypsin inhibitors. (c) 2005 Elsevier Ltd. All rights reserved.

棉花抗虫基因工程研究

本文通过根农杆菌（Agrobacterium tumfaciens）介导法分别将Signal和KDEL修饰的豇豆胰蛋白酶抑制剂（Cowpea trypsin inhibitor, CpTI）基因、豌豆外源凝集素（Pea lectin, P-Lec）和大豆Kunitz型胰蛋白酶抑制剂（Soybean Kunitz typsin inhibitor, SKTI）双价抗虫基因、雪花莲外源凝集素（Galanthus nivals agglutinin, GNA）基因以及高效复合启动子OM控制的苏云金杆菌（Bacillus thuringiensis, B.t.）杀虫毒蛋白基因导入了陆地棉（Gossypium hirsutum L.）栽培品种新陆早1号、新陆中2号、晋棉7号、冀合321、辽9和晋棉12号，并获得了大批转基因再生植株。 实验中对影响棉花转化和再生的一些条件进行了研究，从根农杆菌培养、棉花无菌苗的制备、转化操作和共培养等方面对转化条件进行了探讨;从激素配化、植物表达载体、外植体类型、基因型等方面对抗性愈伤组织的诱导进行了摸索;从激素、从碳源、培养容器、pH值、抗褐化剂及固化剂的选择等方面对影响植株再生的条件进行了优化。 本文开创性地采用嫁接代替移栽，从而极大地提高了转化植株定植成活率，缩短了缓苗时间并增加了转化植株当代的繁殖系数。 在建立了一套较为高效的陆地棉转化及再生系统基础上，本文还进行了其它转化方式和转化体系的初步探讨。利用棉花幼嫩种子无菌苗下胚轴作为外植体，通过改变愈伤组织诱导培养基配方面提高胚性愈伤组织的诱导频率，进而得到更多的体细胞胚状和再生植株，缩短再生周期;尝试用胚性愈伤组织作为外植体的根农杆菌介导法转化，确定了一些与转化有关的条件;建立了一套棉花茎尖培养程序，为运用基因枪法轰击棉花茎尖分生组织或用根农杆菌直接转化茎尖分生组织，以克服根农杆菌转化棉花时体胚发生的基因型局限开辟了一条新途径。 本文还建立了一种快速鉴定转化植株后代的方法。这一简便方法还有助于进行转基因棉纯合系的筛选以及外源基因的遗传稳定性研究。 转基因植株经Npt-II ELISA、PCR、PCR Southern 检测证明外源抗虫基因CpTI、SKTI、P-lec、GNA以及B.t.基因已存在于转化植株基因组内。修饰的CpTI转基因植株抗棉铃虫（Heliothis armigera Hubner）试验结果表明，其杀虫效果显著优于前期未修饰的CpTI转化植株。P－lec和SKTI双价转基因植株抗棉铃虫试验结果表明，转基因植株对棉铃虫幼虫具有较强的杀虫活力。 目前，已获得转以上抗虫基因棉花T1代植株。为今后进一步将植物基因工程技术应用于棉花遗传改良打下了基础。

水稻幼苗脱黄化过程以及灌浆期茎的蛋白质组学研究

水稻既是我国三大粮食作物之一，又是基因组学研究的模式材料，在生产实践和科学研究中都占有极其重要的地位。基因组学研究取得的巨大成就以前所未有的深度和广度推动了生命科学各个研究领域的飞速发展。水稻基因组的破译是水稻科学研究的重要里程碑，同时也宣告了功能基因组学时代的到来。蛋白质组学是研究细胞内全部蛋白质的动态表达及其相互关系的新兴学科，是功能基因组学研究的重要组成部分和战略制高点。 本论文采用高分辨率的蛋白质双向电泳分离技术和高通量的蛋白质质谱分析技术以及生物信息学等手段，开展水稻灌浆期茎蛋白质组表达模式和水稻幼苗脱黄化过程的比较蛋白质组学研究，探讨茎生长发育规律和水稻应答光信号相关蛋白质及其网络调控机制，是学科前沿与实际应用的有机结合，在科研和生产实践中都具有重要的意义。 首先，分别构建了灌浆期水稻顶端茎段和水稻黄化幼苗的蛋白质组表达谱。并对其中185个目的蛋白点进行了MALDI-TOF/MS分析和数据库检索鉴定。共有149个蛋白质得到了鉴定，蛋白质鉴定的成功率为80.5％。这些被鉴定的蛋白质分属118个基因的表达产物，根据它们功能可以分为13种不同的类别，其中绝大多数为能量产生和代谢以及抗性相关的蛋白质。 在水稻灌浆期顶端茎段表达的蛋白质中，与能量和物质代谢相关的蛋白质例如ATPase、磷酸丙糖异构酶，6－磷酸葡萄糖异构酶等占有很高比例，说明茎段组织中具有很强的代谢活动。与生长发育相关的蛋白质包括beta-tubulins、无机焦磷酸酶（inorganic pyrophosphatase）、液泡质子ATP酶（vacuolar proton-ATPase）以及UDP葡萄糖焦磷酸酶等的大量累积，显示出顶端茎段细胞分裂和生长迅速;同时，贮存多糖和结构多糖也在旺盛合成。G蛋白、GDP释放抑制因子等信号传导蛋白以及苯丙氨酸氨解酶、谷胱苷肽S转移酶（glutathione S-transferase，GST）、抗坏血酸过氧化酶（ascorbate peroxidase，APX）以及超氧化物歧化酶（superoxide dismutase，SOD）等抗性相关蛋白质在该时期丰度表达，表明在灌浆期水稻顶端茎段能够迅速感受并传递外界信号，从而使得其在遭受胁迫时能够立刻启动抗逆防御系统，最大限度地降低不利环境对种子发育的影响。 在黑暗中萌发和生长的水稻黄化幼苗随着光照时间（0~24小时）的延长，能通过双向电泳后检测到的蛋白质逐渐变少，24小时后趋于稳定，相当于正常光照条件下生长的水稻幼苗蛋白质组表达谱。进一步分析表明，在黄化苗中，分解代谢及能量产生相关的蛋白如丙糖磷酸异构酶、琥珀酰辅酶A连接酶、异戊酰辅酶A脱氢酶与ATPase等的表达量比较丰富;另外，还可能启动了脂肪酸的α氧化分解途径，以供黑暗中生长所需的物质和能量。当黄化幼苗光照后，与光合作用及物质合成相关的一些蛋白质表达量增加，而那些分解代谢相关酶类则有所下降。同时，鸟核苷酸结合蛋白β亚基类似蛋白、20S proteasome以及Bowman Birk trypsin inhibitor等信号传递及抗性相关蛋白随着光照时间的延长而减少，说明黑暗胁迫条件下水稻幼苗启动了相关的抗逆途径。叶绿素合成途径中的蛋白酶胆色素原脱氨基酶和金属鳌合酶在脱黄化过程中表达量有所下降，可能是因为叶绿素合成产物具有反馈抑制作用。 本研究首次利用蛋白质组学方法来解析水稻灌浆期茎蛋白质组表达模式和水稻黄化幼苗响应光因子的蛋白质组变化情况，鉴定了一些有价值的蛋白质，并得到了它们的表达特点和相关数据，为更好地理解水稻顶端茎秆的生长特点和功效、水稻应答黑暗胁迫和光形态建成以及光合作用机理等提供了分子证据。

金环蛇蛇毒中的一种新型胰蛋白酶抑制剂

目的:从金环蛇蛇毒中分离纯化名为bungaruskunin 1的一种新型胰蛋白酶抑制剂,并从其毒腺的cDNA文库中克隆出该胰蛋白酶抑制剂的cDNA全序列.方法:通过Sephadex G-50, CM-Sephadex C-25, HPLC, RP-HPLC (C4 column)方法分离纯化bungaruskunin 1.样品的丝氨酸蛋白酶抑制剂活性则是在室温条件下50mmol·L-1 Tris-HCl, pH 7.8的缓冲液中通过对显色底物的水解抑制作用来检测的.金环蛇毒腺RNA用TRIZOL提取,并用SMARTM PCR cDNA synthesis kit (Clontech)建成cDNA文库.根据其信号肽的保守区域合成引物从该文库中扩增出bungaruskunin 1的cDNA全序列,进行胶回收,酶连到pMDl8-T载体中转化测序.结果:bungaruskunin 1的前体由83个氨基酸组成,其中信号肽含有24个氨基酸,成熟肽即:bungaruskunin 1合有59个氨基酸.bungaruskunin 1的cDNA序列与从红腹伊澳蛇Pseudechis porphyriacus中分离纯化得到的丝氨酸蛋白酶抑制剂blackelin的cDNA序列的相似性高达64%.bungaruskunin 1是一种含有保守Kunitz端的Kuntiz蛋白酶抑制剂家族的一员,从而能够抑制蛋白酶和弹性酶的活性.在cDNA文库中,我们同时还筛选到了2种新的β-bungarotoxin B链的序列.结论:这些发现很好地证明了蛇中Kunitz/BPTI胰蛋白酶抑制剂和毒性神经的家族可能起源于共同的祖先.

ISOLATION AND PROPERTIES OF A BLOOD-COAGULATION FACTOR-X ACTIVATOR FROM THE VENOM OF KING COBRA (OPHIOPHAGUS HANNAH)

A specific blood coagulation factor X activator was purified from the venom of Ophiophagus hannah by gel filtration and two steps of FPLC Mono-Q column ion-exchange chromatography. It showed a single protein band both in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and alkaline polyacrylamide gel electrophoresis. The mol. wt was estimated to be 62,000 in non-reducing conditions and 64,500 in reducing conditions by SDS-PAGE. The isoelectric point was found to be pH 5.6. The enzyme had weak amidolytic activities toward CBS 65-25, but it showed no activities on S-2266, S-2302, thrombin substrate S-2238, plasmin substrate S-2251 or factor Xa substrate S-2222. It had no arginine esterase activity toward substrate benzoylarginine ethylester (BAEE). The enzyme activated factor X in vitro and the effect was absolutely Ca2+ dependent, with a Hill coefficient of 6.83. It could not activate prothrombin nor had any effect on fibrinogen and thus appeared to act specifically on factor X. The procoagulant activity of the enzyme was almost completely inhibited by serine protease inhibitors like PMSF, TPCK and soybean trypsin inhibitor; partially inhibited by L-cysteine. Metal chelator EDTA did not inhibit its procoagulant activity. These results suggest that the factor X activator from O. hannah venom is a serine protease.

AN ACTIVATOR OF BLOOD-COAGULATION FACTOR-X FROM THE VENOM OF BUNGARUS-FASCIATUS

A specific activator of blood coagulation factor X was purified from the venom of Bungarus fasciatus by gel filtration and by ion-exchange chromatography on a Mono-Q column (FPLC). It consisted of a single polypeptide chain, with a mel. wt of 70,000 in reducing and non-reducing conditions. The enzyme had an amidolytic activity towards the chromogenic substrates S-2266 and S-2302 but it did not hydrolyse S-2238, S2251 or S-2222, which are specific substrates for thrombin, plasmin and factor Xa, respectively. The enzyme activated factor X in vitro and the effect was Ca2+ dependent with a Hill coefficient of 7.9. As with physiological activators, the venom activator cleaves the heavy chain of factor X, producing the activated factor Xa alpha. The purified factor X activator from B. fasciatus venom did not activate prothrombin, nor did it cleave or clot purified fibrinogen. The amidolytic activity and the factor X activation activity of the factor X activator from B. fasciatus venom were readily inhibited by serine protease inhibitors such as diisopropyl fluorophosphate (DFP), phenylmethanesulfonyl fluoride (PMSF), benzamidine and by soybean trypsin inhibitor but not by EDTA. These observations suggest that the factor X activator from B. fasciatus venom is a serine protease. It therefore differs from those of activators obtained from Vipera russelli and Bothrops atrox venoms, which are metalloproteinases.

CHARACTERIZATION OF OHS1, AN ARGININE/LYSINE AMIDASE FROM THE VENOM OF KING COBRA (OPHIOPHAGUS HANNAH)

In this paper, we present the results of purification and characterization of an arginine/lysine amidase from the venom of Ophiophagus hannah (OhS1). It was purified by Sephadex G-75 gel filtration and ion-exchange chromatography on DEAE-Sepharose CL-6B. It is a protein of about 43,000, consisting of a single polypeptide chain. It is a minor component in the venom. The purified enzyme was capable of hydrolysing several tripeptidyl-p-nitroanilide substrates having either arginine or lysine as the C-terminal residue. We studied the kinetic parameters of OhS1 on six these chromogenic substrates. OhS1 did not clot fibrinogen. Electrophoresis of fibrinogen degraded with OhS1 revealed the disappearance of the alpha- and beta-chains and the appearance of lower mel. wt fragments. OhS1 had no hemorrhagic activity. It did not hydrolyse casein, nor did it act on blood coagulation factor X, prothrombin and plasminogen. The activity of OhS1 was completely inhibited by NPGB, PMSF, DFP, benzamidine and soybean trypsin inhibitor, suggesting it is a serine protease. Metal chelator (EDTA) had no effect on it.

Purification and characterization of an irreversible serine protease inhibitor from skin secretions of Bufo andrewsi

Amphibian skin secretions contain many bioactive compounds. In the present work, an irreversible serine protease inhibitor, termed baserpin, was purified for the first time from the skin secretions of toad Bufo andrewsi by Successive ion-exchange and gelfiltration chromatography. Baserpin is a single chain glycoprotein, with an apparent molecular weight of about 60 kDa in SDS-PAGE. Baserpin is an irreversible inhibitor and effectively inhibits the catalytic activity of trypsin, chymotrypsin and elastase. SDS-stable baserpin-trypsin complex could be seen in SDS-PAGE indicates that it possibly belongs to the serpin superfamily. According to the association rates determined, baserpin is a potent inhibitor of bovine trypsin (4.6 X 10(6) M-1 S-1), bovine chymotrypsin (8.9 X 10(6) M-1 s(-1)) and porcine elastase (6.8 X 10(6) M-1 s(-1)), whereas it shows no inhibitory effect on thrombin. The N-terminal sequence of baserpin is HTQYPDILIAKPXDK, which shows no similarity with other known serine protease inhibitors. (c) 2005 Elsevier Ltd. All rights reserved.

A serine proteinase inhibitor from frog eggs with bacteriostatic activity

By Sephadex G-50 gel filtration, Resource Q anionic exchange and C4 reversed phase liquid high performance liquid chromatography, a proteinase inhibitor protein (Ranaserpin) was identified and purified from the eggs of the odour frog, Rana grahami. The protein displayed a single band adjacent to the molecular weight marker of 14.4 kDa analyzed by SDS-PAGE. The inhibitor protein homogeneity and its molecular weight were confirmed again by MALDI-TOF mass spectrometry analysis. The MALDI-TOF mass spectrum analysis gave this inhibitor protein an m/z of 14422.26 that was matched well with the result from SDS-PAGE. This protein is a serine proteinase inhibitor targeting multiple proteinases including trypsin, elastase, and subtilisin. Ranaserpin inhibited the proteolytic activities of trypsin, elastase, and subtilisin. It has an inhibitory constant (K-i) of 6.2 x 10(-8) M, 2.7 x 10(-7) M and 2.2 x 10(-8) M for trypsin, elastase, and subtilisin, respectively. This serine proteinase inhibitor exhibited bacteriostatic effect on Gram-positive bacteria Bacillus subtilis (ATCC 6633). It was suggested that ranaserpin might act as a defensive role in resistance to invasion of pests or pathogens. This is the first report of serine proteinase inhibitor and its direct defensive role from amphibian eggs. (C) 2007 Elsevier Inc. All rights reserved.

Isolation, expression and characterization of a novel dual serine protease inhibitor, OH-TCI, from king cobra venom

Snake venom Kunitz/BPTI members are good tools for understanding of structure-functional relationship between serine proteases and their inhibitors. A novel dual Kunitz/BPTI serine proteinase inhibitor named OH-TCI (trypsin- and chymotrypsin-dual inhibito

A novel serine protease inhibitor from Bungarus fasciatus venom

By Sephadex G-50 gel filtration, cation-exchange CM-Sephadex C-25 chromatography and reversed phase high-performance liquid chromatography (HPLC), a novel serine protease inhibitor named bungaruskunin was purified and characterized from venom of Bungarus fasciatus. Its cDNA was also cloned from the cDNA library of B. fasciatus venomous glands. The predicted precursor is composed of 83 amino acid (aa) residues including a 24-aa signal peptide and a 59-aa mature bungaruskunin. Bungaruskunin showed maximal similarity (64%) with the predicted serine protease inhibitor blackelin deduced from the cDNA sequence of the red-bellied black snake Pseudechis porphyriacus. Bungaruskunin is a Kunitz protease inhibitor with a conserved Kunitz domain and could exert inhibitory activity against trypsin, chymotrypsin, and elastase. By screening the cDNA library, two new B chains of beta-bungarotoxin are also identified. The overall structures of bungaruskunin and beta -bungarotoxin B chains are similar; especially they have highly conserved signal peptide sequences. These findings strongly suggest that snake Kunitz/BPTI protease inhibitors and neurotoxic homologs may have originated from a common ancestor. (c) 2007 Elsevier Inc. All rights reserved.

Purification, characterization and primary structure of a chymotrypsin inhibitor from Naja atra venom

A chymotrypsin inhibitor, designated NA-CI, was isolated from the venom of the Chinese cobra Naja atra by three-step chromatography. It inhibited bovine (x-chymotrypsin with a K-i of 25 nM. The molecular mass of NA-CI was determined to be 6403.8 Da by matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) analysis. The complete amino acid sequence was determined after digestion of S-carboxymethylated inhibitor with Staphylococcus aureus V8 protease and porcine trypsin. NA-CI was a single polypeptide chain composed of 57 amino acid residues. The main contact site with the protease (PI) has a Phe, showing the specificity of the inhibitor. NA-CI shared great similarity with the chymotrypsin inhibitor from Naja naja venom (identities = 89.5%) and other snake venom protease inhibitors. (C) 2003 Elsevier Inc. All rights reserved.