Takei Y, Silldorff E P, Hasegawa Y, Watanabe T X, Nakajima K, Stephens G A, Sakakibara S
Department of Physiology, Kitasato University School of Medicine, Kanagawa, Japan.
Gen Comp Endocrinol. 1993 May;90(2):214-9. doi: 10.1006/gcen.1993.1076.
Angiotensin I (ANG I) of the American alligator Alligator mississippiensis was isolated from incubates of homologous plasma and kidney extract, and its amino acid sequence was determined as H-Asp-Arg-Val-Tyr-Val-His-Pro-Phe-Ala-Leu-OH. The presence of strongly hydrophobic alanine at position 9 is unusual among ANGs I sequenced to date. Since alanine can be converted to serine by a one-point mutation of the triplet nucleotides, the phylogenetic proximity of the alligator to birds, whose ANG I has serine at position 9, is confirmed by the chemical evolution of the hormone structure. The alligator [Asp1,Val5,Ala9] ANG I increased arterial blood pressure of conscious alligators, but it was no more potent than avian [Asp1,Val5,Ser9] ANG I. The alligator ANG I was also equipotent to the homologous ANG I in the quail and rat. It is concluded that substitutions at position 9 have little influence on the vasopressor activity of ANG I.
美洲短吻鳄（密西西比鳄）的血管紧张素I（ANG I）是从同源血浆和肾脏提取物的孵育物中分离出来的，其氨基酸序列被确定为H-Asp-Arg-Val-Tyr-Val-His-Pro-Phe-Ala-Leu-OH。在迄今为止测序的ANG I中，第9位存在强疏水性丙氨酸是不寻常的。由于丙氨酸可以通过三联体核苷酸的单点突变转化为丝氨酸，因此通过激素结构的化学进化证实了短吻鳄与鸟类在系统发育上的接近性，鸟类的ANG I在第9位是丝氨酸。短吻鳄的[Asp1,Val5,Ala9] ANG I可提高清醒短吻鳄的动脉血压，但它的效力并不比鸟类的[Asp1,Val5,Ser9] ANG I更强。短吻鳄的ANG I在鹌鹑和大鼠中与同源ANG I的效力也相当。得出的结论是，第9位的取代对ANG I的血管升压活性影响很小。
