Molecular studies cDNAs

The expression of many of these molecules has been studied during various stages of differentiation of normal neutrophils and also of corresponding leukemic cells employing molecular biology techniques (eg, measurements of their specific mRNAs). For the majority, cDNAs have been isolated and sequenced, amino acid sequences deduced, genes have been localized to specific chromosomal locations, and exons and intron sequences have been defined. Some important proteinases of neutrophils are listed in Table 52-12. 

The wound-induced synthesis and accumulation of proteinase Inhibitors I and II in tomato leaves has provided a model system to study the regulation of proteinase inhibitor genes in plants. The simplicity of the phenomenon has made it possible to Isolate the wound-factor, or hormone, and to study its release, direction and rate of transport in tomato plants. Messenger RNA has been isolated from leaves of wounded plants and contains translatable mRNAs for the two proteinase inhibitors. Studies with these mRNAs have provided a basis for the initiation of a program to clone inhibitor cDNAs for studies of the molecular basis of the wound-Induced process of inhibitor synthesis. 

A sheep blastocyst library was screened with a probe based on the N-terminal sequence of the IFN-T protein and the cDNA obtained (Table 3). Surprisingly, it exhibited 45-55% homology with various IFNs from human, mouse, rat, and pig and 70% homology with bovine IFN-co [12]. It shared both molecular weight (19 kDa) and pi (5.4-5.6) with IFN-as, while its length, 172 amino acids, was equivalent to the IFN-cos. In competition studies, IFN-T was found to compete with IFNs a, (3, and for binding to the Type IIFN receptor [13]. In contrast, IFN-T exhibited several unique properties such as its reproductive function, its poor inducibility by virus, and its apparent reduced cytotoxicity. Thus, IFN- conceptus protein appears to be a novel IFN. 

CYP2C18 has been examined as a candidate for the (S)-mephenytoin 4 -hydroxylase polymorphism. Romkes et al. (1991) demonstrated that cDNA-expressed CYP2C18 4 -hydroxylated (5)-mephenytoin at a rate above background. However, CYP2C19 has recently been established as the protein responsible for the (5)-mephenytoin 4 -hydroxylase polymorphism (Wrighton et al., 1993 Goldstein et al., 1994). Population studies have demonstrated that 3-5% of Caucasians and about 20% of Asians are poor metabolizers of (5)-mephenytoin (Kalow, 1986). The molecular basis for this polymorphism has recently been established (de Morals et al., 1994). 

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