RESUMO
Guinea pig high-molecular-weight and low-molecular-weight (HMW and LMW) kininogen cDNA were amplified from liver mRNA by RT-PCR. Their nucleotide sequences were analyzed and deduced to amino acid sequences. The HMW kininogen, composed of 607 amino acid residues with a 18-residue signal sequence, possessed the cysteine protease inhibitor domains I and II, the bradykinin domain, the histidine-rich region, and the prekallikrein-binding region. The amino acid sequence preceding the bradykinin domain was found not to be -Leu-Met-Lys- but -Leu-Thr-Arg-. Therefore, kallidin (Lys-bradykinin) and Met-kallidin are not liberated from the guinea pig kininogens. We purified the HMW kininogen protein from plasma and prepared the kinin-free form using guinea pig plasma kallikrein. Although the amino-terminal of the HMW kininogen was modified, the 25 amino-terminal residues of the light chain of the kinin-free kininogen corresponded to the deduced sequence just after the bradykinin moiety of the HMW kininogen. With regard to the LMW kininogen, the nucleotide sequence down to T(1200) as well as the amino acid sequence till Thr(382) was identical to that of the HMW kininogen. We also examined the localization of the guinea pig kininogen gene on the prometaphase lymphocyte chromosomes by fluorescence in situ hybridization method. Two pair signals were observed on a pair of homologous chromosomes, each of which is composed of two chromatids. Based on these findings, we concluded that HMW and LMW kininogens are produced from the single kininogen gene in guinea pig as in the cases of the other mammalian species reported so far.
Assuntos
Cininogênio de Alto Peso Molecular/química , Cininogênio de Baixo Peso Molecular/química , Sequência de Aminoácidos , Animais , Sequência de Bases , Bovinos , Mapeamento Cromossômico , Cobaias , Humanos , Hibridização in Situ Fluorescente , Técnicas In Vitro , Cininogênio de Alto Peso Molecular/genética , Cininogênio de Baixo Peso Molecular/genética , Fígado/química , Dados de Sequência Molecular , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Especificidade da Espécie , BaleiasRESUMO
Kininogens serve dual functions by forming a scaffold for the assembly of the protein complex initiating the surface-activated blood coagulation cascade and as precursors for the kinin hormones. While rats have three kininogen genes, for mice, cattle, and humans only one gene has been described. Here, we present sequence and expression data of a second mouse kininogen gene. The two genes, kininogen-I and kininogen-II, are located in close proximity on chromosome 16 in a head-to-head arrangement. In liver and kidney, both genes are expressed and for each gene three alternative splice variants are synthesized. Two of them are the expected high and low molecular weight isoforms known from all mammalian kininogens. However, for both genes also a third, hitherto unknown splice variant was detected which lacks part of the high molecular weight mRNA due to splicing from the low molecular weight donor site to alternative splice acceptor sites in exon 10. The physiological functions of the six kininogen isoforms predicted by these findings need to be determined.
Assuntos
Regulação da Expressão Gênica/fisiologia , Cininogênios/química , Cininogênios/genética , Processamento Alternativo , Sequência de Aminoácidos , Animais , Sequência de Bases , Ordem dos Genes , Cininogênio de Alto Peso Molecular/química , Cininogênio de Alto Peso Molecular/genética , Cininogênio de Baixo Peso Molecular/química , Cininogênio de Baixo Peso Molecular/genética , Cininogênios/biossíntese , Cininogênios/isolamento & purificação , Masculino , Camundongos , Dados de Sequência Molecular , Isoformas de Proteínas/biossíntese , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/isolamento & purificaçãoRESUMO
Adsorbed proteins on biomaterial surfaces determine whether cells adhere, but rheological variables are also critical. Neutrophil adhesion under well-defined radial flow conditions was studied on glass preadsorbed with plasma proteins or plasma protein domain fragments. Fibrinogen, low-molecular-weight kininogen (LK), high-molecular-weight kininogen (HK), cleaved HK (HKa), and recombinant HK domains 3 and 5 (D3 and D5H) were used. The number of adherent cells on the HK and HKa surfaces was less than 10% that found on the fibrinogen absorbed surface. The degree of spreading was minimal and detachment of adherent neutrophils was observed. HK and HKa contain binding sites for both anionic surfaces and neutrophils in the same domain (D5H). When adsorbed to surfaces, HK and HKa did not have the neutrophil binding sites available and therefore exhibited an anti-adhesive effect. Although D5H contains anionic surface binding sites, its small molecular size required a higher number of adsorbed molecules to cover the surface before a significant decrease in cell adhesion was observed. Since LK and D3 do not possess specific anionic surface binding sites, the adsorption of these proteins on glass was very low compared to HK and HKa. Thus, extensive cell adhesion and spreading were observed on the surfaces partially covered with preadsorbed LK and D3.
