Phylogeny of vertebrate Src tyrosine kinases revealed by the epitope region of mAb327.
Mass fingerprinting and MS/MS analysis demonstrated that Xyk, a 57-kDa Src family tyrosine kinase that is activated within minutes of Xenopus egg fertilization, comprises a mixture of two Src proteins, Src1 and Src2. However, the Xenopus Src protein, denoted as xSrc, is hardly detectable with mAb327, a universal Src-specific antibody, whose target sequence has not yet been determined. We show that a point amino acid substitution in the Src homology 3 domain of xSrc is critical for improvement of the low efficiency of its recognition by mAb327. Namely, a point-mutated xSrc, in which Arg-121 was replaced by His that is conserved among mAb327-reactive Src in mammals and chicken, showed increased recognition by mAb327. On the other hand, a mutant chicken Src, in which the His-122 residue is replaced by Arg, showed decreased recognition by mAb327. Genomic sequencing analysis also demonstrated that reptile Src proteins are of either the R-type (snake) or H-type (caiman, turtle, and tortoise). These studies revealed, for the first time, a critical amino acid in the Src SH3 domain for mAb327 recognition, and suggest a novel scheme for the molecular evolution of Src, in which the H-type Src(s) are monophyletic and derived from the R-type Src.
Research Center for Environmental Genomics, Kobe University, Nada, Kobe 657-8501. tiwasaki@kobe-u.ac.jp
Tetsushi
T
Iwasaki
Ken-Ichi
K
Sato
Ken-Ichi
K
Yoshino
Shuji
S
Itakura
Keiko
K
Kosuge
Alexander A
AA
Tokmakov
Koji
K
Owada
Kazuyoshi
K
Yonezawa
Yasuo
Y
Fukami
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology*; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D000939:Epitopes / Q000276:immunology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D014982:Xenopus laevis; D019061:src-Family Kinases / Q000235:genetics* / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D019061:src-Family Kinases