Andrews P C, Dixon J E
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
Biochemistry. 1987 Jul 28;26(15):4853-61. doi: 10.1021/bi00389a037.
Major products and an intermediate in the proteolytic processing pathway of preprosomatostatin I from anglerfish (Lophius americanus) were purified and characterized. Proteolytic mapping by fast atom bombardment mass spectrometry was used to rapidly locate regions of the peptides whose masses deviated from those deduced from the cDNA sequence. Amino acid analysis and partial Edman sequencing were also used to confirm the structures. The protein structural data indicate a Glu for Gly substitution at position 83 of preprosomatostatin I (aPPSS-I, numbering from the initiator Met) relative to the cDNA sequence. Two of the peptides isolated, aPPSS-I (26-52) (7.5 nmol X g-1) and aPPSS-I (26-92) (49.5 nmol X g-1), define signal cleavage as occurring between Cys-25 and Ser-26. A partial sequence was obtained from fragment ions in the mass spectrum of a peptide corresponding to aPPSS-I (94-105) (58 nmol X g-1). The 14-residue somatostatin [SS-14 corresponding to aPPSS-I (108-121)] has previously been isolated [Noe, B. D., Spiess, J., Rivier, J. E., & Vale, W. (1979) Endocrinology (Baltimore) 105, 1410-1415]. Taken together, these peptides suggest a pathway for prosomatostatin I processing in which the residues corresponding to SS-14 and the immediately preceding 14 residues are cleaved from the prohormone via endoproteolysis (order of cleavage not determined). The fragment aPPSS-I (94-105) was isolated in lower yield than SS-14 and may represent a secondary site of cleavage. Subsequent cleavage at arginine-53 results in the minor peptide aPPSS-I (26-52).(ABSTRACT TRUNCATED AT 250 WORDS)
对美洲安康鱼（Lophius americanus）前促生长抑素I蛋白水解加工途径中的主要产物及一种中间体进行了纯化和表征。采用快原子轰击质谱法进行蛋白水解图谱分析，以快速定位肽段中质量与cDNA序列推导值不同的区域。氨基酸分析和部分埃德曼测序也用于确认结构。蛋白质结构数据表明，相对于cDNA序列，前促生长抑素I（aPPSS-I，从起始甲硫氨酸开始编号）第83位的甘氨酸被谷氨酸取代。分离得到的两种肽段，aPPSS-I（26 - 52）（7.5 nmol X g-1）和aPPSS-I（26 - 92）（49.5 nmol X g-1），确定信号肽切割发生在半胱氨酸-25和丝氨酸-26之间。从对应于aPPSS-I（94 - 105）（58 nmol X g-1）的肽段质谱中的碎片离子获得了部分序列。此前已分离出14个氨基酸的生长抑素[对应于aPPSS-I（108 - 121）的SS-14][诺伊，B.D.，斯皮斯，J.，里维埃，J.E.，& 瓦尔，W.（1979年）《内分泌学》（巴尔的摩）105，1410 - 1415]。综合来看，这些肽段提示了前生长抑素I的加工途径，其中对应于SS-14及紧接其前的14个残基通过内蛋白水解作用从激素原上切割下来（切割顺序未确定）。片段aPPSS-I（94 - 105）的分离产率低于SS-14，可能代表一个次要的切割位点。随后在精氨酸-53处切割产生了小肽段aPPSS-I（26 - 52）。（摘要截短至250字）
