Gehrig P M, Krzyzaniak A, Barciszewski J, Biemann K
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, 02139, USA.
Proc Natl Acad Sci U S A. 1996 Apr 16;93(8):3647-52. doi: 10.1073/pnas.93.8.3647.
The amino acid sequences of a number of closely related proteins ("napin") isolated from Brassica napus were determined by mass spectrometry without prior separation into individual components. Some of these proteins correspond to those previously deduced (napA, BngNAP1, and gNa), chiefly from DNA sequences. Others were found to differ to a varying extent (BngNAP1', BngNAP1A, BngNAP1B, BngNAP1C, gNa', and gNaA). The short chains of gNa and gNa' and of BngNAP1 and BngNAP1' differ by the replacement of N-terminal proline by pyroglutamic acid; the long chains of gNaA and BngNAP1B contain a six amino acid stretch, MQGQQM, which is present in gNa (according to its DNA sequence) but absent from BngNAP1 and BngNAP1C. These alternations of sequences between napin isoforms are most likely due to homologous recombination of the genetic material, but some of the changes may also be due to RNA editing. The amino acids that follow the untruncated C termini of those napin chains for which the DNA sequences are known (napA, BngNAP1, and gNa) are aromatic amino acids. This suggests that the processing of the proprotein leading to the C termini of the two chains is due to the action of a protease that specifically cleaves a G/S-F/Y/W bond.
通过质谱法测定了从甘蓝型油菜中分离出的多种密切相关蛋白质（“napin”）的氨基酸序列，无需事先将其分离成单个成分。这些蛋白质中的一些与先前主要从DNA序列推导出来的蛋白质（napA、BngNAP1和gNa）相对应。其他蛋白质则被发现存在不同程度的差异（BngNAP1'、BngNAP1A、BngNAP1B、BngNAP1C、gNa'和gNaA）。gNa和gNa'以及BngNAP1和BngNAP1'的短链因N端脯氨酸被焦谷氨酸取代而有所不同；gNaA和BngNAP1B的长链包含一段六个氨基酸的序列MQGQQM，该序列存在于gNa中（根据其DNA序列），但在BngNAP1和BngNAP1C中不存在。napin同工型之间的这些序列变化很可能是由于遗传物质的同源重组，但其中一些变化也可能是由于RNA编辑。对于已知DNA序列的那些napin链（napA、BngNAP1和gNa），其未截断的C端之后的氨基酸是芳香族氨基酸。这表明导致两条链C端的前体蛋白加工是由于一种特异性切割G/S - F/Y/W键的蛋白酶的作用。
