1. A novel bradykinin-related peptide from skin secretions of toad Bombina maxima and its precursor containing six identical copies of the final product
R Lai, H Liu, W Hui Lee, Y Zhang Biochem Biophys Res Commun. 2001 Aug 17;286(2):259-63. doi: 10.1006/bbrc.2001.5359.
Amphibian skin contains rich bradykinin-related peptides, but the mode of biosynthesis of these peptides is unknown. In the present study, a novel bradykinin-related peptide, termed bombinakinin M, was purified from skin secretions of the Chinese red belly toad Bombina maxima. Its primary sequence was established as DLPKINRKGPRPPGFSPFR that comprises bradykinin extended from its N-terminus by a 10-residue segment DLPKINRKGP. The cDNA structure of bombinakinin M was found to contain a coding region of 624 nucleotides. The encoded precursor of bombinakinin M is composed of a signal peptide, an acidic peptide, six 100% identical copies of a 28-amino-acid peptide unit including bombinakinin M plus a spacer peptide. The sequence of bombinakinin M is preceded by a single basic residue (arginine), which represents the site of cleavage for releasing of mature bombinakinin M. This is the first cDNA cloning of bradykinin-related peptides from amphibian skin. The unique cDNA structure encoding bombinakinin M suggests that the generation modes of bradykinin-related peptides in amphibian skin and in mammalian blood system are different.
2. Cloning of bradykinin precursor cDNAs from skin of Bombina maxima reveals novel bombinakinin M antagonists and a bradykinin potential peptide
Wen-Hui Lee, Shu-Bai Liu, Ji-Hong Shen, Yang Jin, Yun Zhang Regul Pept. 2005 Apr 15;127(1-3):207-15. doi: 10.1016/j.regpep.2004.12.002.
Bombinakinin M (DLPKINRKGP-bradykinin) is a bradykinin-related peptide purified from skin secretions of the frog Bombina maxima. As previously reported, its biosynthesis is characterized by a tandem repeats with various copy numbers of the peptide and sometimes co-expressed with other structure-function distinguishable peptides. At present study, two novel cDNAs encoding bombinakinin M and its variants were cloned from a cDNA library from the skin of the frog. The encoded two precursor proteins are common in that each contains three repeats of a novel 16-amino acid peptide unit and one copy of kinestatin at their N- and C-terminal parts, respectively. They differ in that the first precursor contains two copies of bombinakinin M and the second one contains one copy of a novel bombinakinin M variant. Bombinakinin M was found to elicit concentration-dependent contractile effects on guinea pig ileum, with an EC50 value of 4 nM that is four times higher than that of bradykinin (1 nM). Interestingly, the synthetic peptide (DYTIRTRLH-amide), as deduced from the 16-amino acid peptide repeats in the newly cloned cDNAs, possessed weak inhibitory activity on the contractile effects of bombinakinin M, but not on that of bradykinin. Furthermore, the newly identified bombinakinin M variant (DLSKMSFLHG-Ile1-bradykinin), did not show contractile activity on guinea pig ileum, but showed potentiation effect on the myotropic activity of bradykinin. In a molar ratio of 1:58, it augmented the activity of bradykinin up to two-fold.
3. Pharmacological Effects of a Novel Bradykinin-Related Peptide (RR-18) from the Skin Secretion of the Hejiang Frog ( Ordorrana hejiangensis) on Smooth Muscle
Xiaowei Zhou, Jie Xu, Ruimin Zhong, Chengbang Ma, Mei Zhou, Zhijian Cao, Xinping Xi, Chris Shaw, Tianbao Chen, Lei Wang, Hang Fai Kwok Biomedicines. 2020 Jul 17;8(7):225. doi: 10.3390/biomedicines8070225.
Bradykinin (BK) and bradykinin-related peptides (BRPs), which were identified from a diversity of amphibian skin secretions, exerted contractile and relaxing effects on non-vascular and vascular smooth muscle, respectively. Here, we report a novel bradykinin-related peptide with a molecular mass of 1890.2 Da, RVAGPDKPARISGLSPLR, which was isolated and identified from Ordorrana hejiangensis skin secretions, followed by a C-terminal extension sequence VAPQIV. The biosynthetic precursor-encoding cDNA was cloned by the "shotgun" cloning method, and the novel RR-18 was identified and structurally confirmed by high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS). Subsequently, the myotropic activity of the synthetic replicate of RR-18 was investigated on the rat bladder, uterus, tail artery and ileum smooth muscle. The peptide was named RR-18 in accordance (R = N-terminal arginine, R = C-terminal arginine, 18 = number of residues). In this study, the synthetic replicates of RR-18 showed no agonist/antagonism of BK-induced rat bladder and uterus smooth muscle contraction. However, it displayed an antagonism of bradykinin-induced rat ileum contraction and arterial smooth muscle relaxation. The EC50 values of BK for ileum and artery, were 214.7 nM and 18.3 nM, respectively. When the tissue was pretreated with the novel peptide, RR-18, at the maximally effective concentration of bradykinin (1 × 10-6 M), bradykinin-induced contraction of the ileum and relaxation of the arterial smooth muscle was reduced by 50-60% and 30-40%, respectively. In conclusion, RR-18 represents novel bradykinin antagonising peptide from amphibian skin secretions. It may provide new insight into possible treatment options for chronic pain and chronic inflammation.
