Cloning and sequence analysis of candidate human natural killer-enhancing factor genes

Abstract

A cytosol factor from human red blood cells enhances natural killer (NK) activity. This factor, termed NK-enhancing factor (NKEF), is a protein of 44,000 M(r) consisting of two subunits of equal size linked by disulfide bonds. NKEF is expressed in the NK-sensitive erythroleukemic cell line K562. Using an antibody specific for NKEF as a probe for immunoblot screening, we isolated several clones from a lambda gt11 cDNA library of K562. Additional subcloning and sequencing revealed that the candidate NKEF cDNAs fell into one of two catagories of closely related but non-identical genes, referred to as NKEF A and B. They are 88% identical in amino acid sequence and 71% identical in nucleotide sequence. Southern blot analysis suggests that there are two to three NKEF family members in the genome. Analysis of predicted amino acid sequences indicates that both NKEF A and B are cytosol proteins with several phosphorylation sites each, but that they have no glycosylation sites. They are significantly homologous to several other proteins from a wide variety of organisms ranging from prokaryotes to mammals, especially with regard to several well-conserved motifs within the amino acid sequences. The biological functions of these proteins in other species are mostly unknown, but some of them were reported to be induced by oxidative stress. Therefore, as well as for immunoregulation of NK activity, NKEF may be important for cells in coping with oxidative insults.

Oxidative and nitrosative stress induces peroxiredoxins in pancreatic beta cells

“…The reduction of peroxynitrite was shown to be fast enough to forestall the oxidation of bystander molecules such as DNA [66]. Peroxiredoxins are at least twice as effective as catalase in protecting glutamine synthetase from inactivation [33,41]. The overexpression of both Prx I and Prx II protected fibroblasts and lymphoma cells against oxidant-induced apoptosis [27,67].…”

“…This is reflected by the numerous synonyms used. Thus Prx I is further known as MSP23 (mouse macrophage stress protein M r 23 K) [30], OSF3 (mouse osteoblast specific factor 3) [31], HBP23 (heme-binding protein M r 23 K) [32], PAG (proliferation-associated gene) [10] and NKEF-A (human natural killer cell-enhancing factor-A) [33]. Prx I is a physiological inhibitor of cAbl kinase activity [34].…”

“…It is also named thiol-specific antioxidant (TSA) [38,39], protector protein (PRP) [11,26], human natural killer cell-enhancing factor-B (NKEF-B) [33,41,40], calpromotin [19,42,43] and torin [44]. Prx II is important in erythroid cell differentiation [11,26] and protects red blood cell membranes from peroxidation [20,45].…”

Structure, organization and expression of common carp (Cyprinus carpio L.) NKEF-B gene

“…Thereby, the NK cells do not recognize presented antigens, and their cytotoxicity occurs more early than Tc cells. NK activity is influenced by various cellular and humoral components in the blood [4].…”

“…NKEF belongs to a new class of highly conserved peroxiredoxin gene family (Prx, containing six members) found in various organisms from prokaryotes to mammals [4]. In human, NKEF is a protein of 44 kDa consisting of two subunits of equal size linked by disulfide bonds.…”