Peptides in rat brain immunoreactive for the amino terminus of cholecystokinin 33: distribution and chromatography

Antisera directed against the amino-terminus of porcine CCK 33 detects related immunoreactivity in rat brain extracts, the distribution of which follows that of CCK 8. Sephadex chromatography indicates that several immunoreactive peptides are present with a molecular weight range of 2600-3500. These peptides are likely to be CCK 39 or CCK 33 and the amino terminal segments of CCK 39/33 without the CCK 8 sequence. The presence of CCK 39/33 and its amino-terminal fragments without CCK 22 and its amino-terminal fragments confirms the absence of CCK 22 in the rat brain. This cleavage at CCK 22 is one of the major differences between the processing of CCK in rat brain and gut and may reflect differences in their physiological roles.     

Peptides in rat brain immunoreactive for the carboxyl terminal extension of cholecystokinin: distribution and chromatography

Utilizing an antiserum raised against a peptide fragment identical to part of the carboxyl terminal extension of cholecystokinin (CCK) predicted by the sequence of CCK mRNA [7], an antiserum has been generated which does not detect CCK 39, CCK 33, CCK 8, CCK 4 or gastrin 171. This antiserum detects several peptides in rat brain, one similar in size to CCK 33 and another slightly larger than CCK 8. These peptides may represent carboxyl-terminally extended forms of CCK, though their chemical structure has not been determined. These peptides are present in all brain regions where CCK 8 can be detected. The abundance of these peptides, their localization in CCK terminal regions, and their enrichment in synaptosome preparations [1] imply that the tryptic cleavage and amidation reaction occur late in the processing of CCK (as has been observed for other biologically active peptides), and probably occur in the synaptic vesicle.     

贻贝抗菌肽的研究进展

贻贝中存在多种抗菌肽,根据一级结构的不同分为4种：defensin(防卫肽)、mytilin、myticin和mytimycin。抗菌肽以前体的形式存在,在缺乏感染等刺激物的情况下。成熟前体以活性方式储存在血液中,当受到感染后便参与组织反应。它们的抗感染反应与哺乳动物吞噬细胞的作用相似,不同的抗菌肽具有不同的抗菌谱。抗菌肽是机体在进化过程中非特异性免疫系统中的一种。     

Peptides in the ribosomal tunnel talk back

In this issue of Molecular Cell, Ramu et?al. demonstrate that nascent peptides located within the ribosomal tunnel can talk back to the peptidyl transferase center to induce translational stalling by restricting the species of aminoacyl-tRNAs that can bind there.     

细胞穿膜肽的研究进展

细胞穿膜肽是一类能携带大分子物质进入细胞的短肽,其穿膜能力不依赖经典的胞吞作用。经过对天然存在的细胞穿膜肽的生物化学性质研究,已经逐渐掌握了细胞穿膜肽的一些共有特性,这类物质均为带有正电荷的长短不等的多肽片段,其中富含精氨酸、赖氨酸等碱性氨基酸残基,二级结构皆具有α-螺旋的空间构象。利用这些特性,目前已人工合成了穿透力更强、效率更高的穿膜肽PEP-1、MPG,并且成功地携带大分子物质进入细胞发挥生物学活性。     

抗真菌肽研究进展

有害真菌已造成植物真菌病害、食物污染和人类真菌感染等问题,给人们的生活和生产带来极大危害,且其逐渐增加对抗真菌药物的耐药性,导致真菌防治日益困难.传统的合成类抗真菌药物具有药物残留和毒副作用,已不能满足需求,作为生物机体天然防御分子的抗真菌肽已成为应对真菌危害及耐药性的重要研究对象.抗真菌肽能够抑制有害真菌,具有高效、...     

Peptides comprising the bulk of rat brain extracts: isolation, amino acid sequences and biological activity.

Chromatographic separation of rat brain extracts followed by automatic Edman sequencing of the major individual components resulted in identification of 61 endogenous peptides derived from known functional proteins (hemoglobin, myelin basic protein, cytochrome-c oxidase, etc.) or unknown precursors. The results are compared with the data obtained earlier for bovine brain. Although the sequences of bovine and rat hemoglobin contain about 20% of amino acid substitutions, the families of structurally related peptides are very similar in both extracts. Several other proteins also give rise to identical or closely related peptide fragments in the two mammalian species. The outlined similarity extends almost exclusively to the most abundant peptides present in the extracts. The minor components show less overlap. Four hemoglobin-derived peptides isolated from rat brain were shown to be biologically active in tumor cells. Eleven are identical to bioactive peptides from other species. Ten structurally overlap with bioactive peptides from other sources. The data obtained show similar biosynthetic pathways of pool components in different species, the resultant peptides being aimed at fulfilling related functions.     

Isolation of Tryptic Peptides from the lie Chain of Ricin D and the Sequences of Some Tryptic Peptides Including N- and C-Terminal Peptides

Twenty tryptic peptides were isolated from the performic acid-oxidized He chain of ricin D by Dowex 1 × 2 column chromatography followed by paper chromatography. The amino acids contained in these peptides accounted for 218 out of 266 residues in the whole protein. The amino acid sequences of nine peptides were determined by manual liquid phase or automatic solid phase Edman degradation, and N- and C-terminal sequences of the He chain of ricin D were established to be NH₂–Ile–Phe–Pro–Lys–Gln–Tyr–Pro–Ile–Ile– and Cys–Ala–Pro–Pro–Pro–Ser–Ser–Gln–Phe, respectively.     

Peptides and neurotransmission in the central nervous system

Radioimmunoassays of brain extracts have shown that several peptides occur in high concentrations in the CNS. The releasing-factor peptides TRF, LRF, somatostatin, CRF and GRF have the highest concentration in the hypothalamic extracts. High levels of somatostatin, CCK octapeptide, neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) are found in cortical extracts. Substance P, CCK, NPY, and enkephalins are present in high concentrations in basal ganglia and mesolimbic areas. Pharmacological doses of these peptides result in several behavioural and vegetative effects. Immunocytochemical studies show that the CNS peptides are localised in neurones and in synaptic vesicles. In vitro studies with brain tissues show that peptides are capable of modifying the ongoing classical neurotransmission. In depressive patients several neuropeptides (CCK, CRF and NPY) have been shown to have low CSF levels. Patients dying of senile dementia have low cortical levels of somatostatin, CRF and substance P. In schizophrenic patients CCK peptides have shown to improve some symptoms. At present the therapeutic potentials of peptides are poorly known. More studies are required to understand their role in neurotransmission and related pathological states.     

RFamide Peptides in the Leech, Hirudo medicinalis

RFamide peptides have been localized to a number of neuronsof the CNS of the leech, Hirudo medicinalis, using immunocytochemicaltechniques. The majority of this immunoreactivity appears tobe due to the peptide FMRFamide. Most of the identified RFamideimmunoreactive cells are cholinergic motor neurons, though someare interneurons. Superfused FMRFamide is active on the targetsof these identified neurons; in a few well studied cases, ithas been possible to show that FMRFamide mimics a specific physiologicalaction of an identified neuron on its target. In the leech as in other phyla where they occur, RFamide peptidesare widely distributed in neurons, and are neuromodulators withdiverse physiological effects.     

中国家蚕抗菌肽CBM1、CBM2的克隆和表达研究

根据所测定的中国产家蚕CBM1和CBM2 cDNA序列,设计成熟肽的特异性引物,将此基因与凝血因子Xa（FXa）的切割序列以PCR方法连接起来,克隆至pGEX—KG表达质粒中。该载体为改进的GST融合表达质粒,所携带的6个Gly有助于提高FXa的切割效率。克隆得到的融合载体在大肠杆菌JM109中扩增和筛选。经DNA测序,证实为含有正确序列的乙酰化的pGEX—KG—FXa—NCBM1（pKG—FXa—NCBM1）、非乙酰化的pGEX—KG—FXa—CBM1（pKG—FXa—CBM1）和乙酰化的pGEX—KG—FXa—NCBM2（pKG—FXa—NCBM2）、非乙酰化的pGEX—KG—FXa—CBM2（pKG—FXa—CBM2）。将该载体在BL21中诱导表达,得到GST-FXa切割位点NCBM1、CBM1、NCBM2、CBM2等4种融合蛋白。经SDS—PAGE,考马斯亮兰染色后,Lab—Work扫描,其表达产物达到15％～20％,每升培养液平均可得20mg融合蛋白。菌体总蛋白经GST-亲和层析柱得到纯的GST—FXa—NCBM1、GST—FXa—CBM1、GST—FXa—NCBM2、GST—FXa—CBM2融合蛋白,再经FXa酶切后,透析过柱得到重组的NCBM1和CBM1。平板抑菌试验证明,4种融合蛋白均有明显的生物学活性,且没有显著的差异。