Resumo

VELOSO, D.. Evidence for the presence of a kininogen-like species in a case of total deficiency of low and high molecular weight kininogens. Braz J Med Biol Res [online]. 1998, vol.31, n.7, pp. 901-910. ISSN 1414-431X.  http://dx.doi.org/10.1590/S0100-879X1998000700004.

Low and high molecular weight kininogens (LK and HK), containing 409 and 626 amino acids with masses of ~65 and 120 kDa after glycosylation, respectively, are coded by a single gene mapped to the human chromosome 3 by alternative splicing of the transcribed mRNA. The NH₂-termini Glu¹-Thr³⁸³ region, identical in LK and HK, contains bradykinin (BK) moieties Arg³⁶³-Arg³⁷¹. LK, HK and their kinin products Lys-BK and BK are involved in several biologic processes. They are evolutionarily conserved and only 7 patients, all apparently normal, have been reported to lack them. In one of these patients (Williams' trait), a codon mutation (Arg¹⁷⁸ ® stop) has been blamed for the absence of LK and HK. However, using Western blots with 2 monoclonal anti-HK antibodies, one that recognizes the region common to LK and HK and the other that recognizes only HK, I detected ~110-kDa bands in the plasma of this LK/HK-deficient patient vs ~120-kDa bands in normal human and ape plasmas. With polyclonal anti-Lys-BK antibody, which strongly detects BK cleaved at its COOH-terminus in purified HK, I detected ~110-kDa bands in the normal and the deficient plasmas. Western blots with a monoclonal anti-prekallikrein (PK) antibody showed that surface activation of PK and distribution of PK activation products, both dependent on HK, were similar in these plasmas. These findings suggest that a mutant gene yielded a kininogen-like species possibly involving aberrant mRNA splicing - structurally different from normal HK, but apparently with the capacity to carry out seemingly vital HK functions.

Palavras-chave : kininogen deficiency; kinins; antibodies; plasma; kininogen-like species; human and nonhuman primates.