Microbial lectin cofunction with lytic activities as a model for a general basic lectin role

Abstract

Lectins are ubiquitous proteins, which exhibit a specific and reversible sugar-binding activity. They react with glycosylated macromolecules and cells and may coaggragate them and lead to their lysis or alterations. Various lectin biological effects are well known, but their basic biological function is considered as yet unknown. In the present review, an experimental evidence and theoretical considerations are forwarded for supporting our suggestion that the general basic lectin or lectinoid (lectin-like protein) function in microorganisms, plants and animals is a cofunction enabling the activities of key lytic enzymes (lysins: glycosidases, proteases, esterases, phosphatases, hemolysin, etc.). The lectin service is: homing onto glycosylated receptors, anchoring to them and induction of cooperative conformational effects which enable their counterpart lysin activity on exogenous or endogenous target molecules and cells. The 'lectin-lysin' pair may reside in the same molecule, or in linked subunits. It may also be formed by cofunction of two separate entities originating from one or two (homogenous or heterogenous) cell sources. The lectin and lysin may be free or cell-bound components located intra or extracellularly. The final result of their cofunction is practically irreversible; either cell and macro-molecule lysis for nutrition, homeostasis and protection or cell alteration, reorganization and new productivity. Our suggestion emphasizes the prominent analogy of lectins to lytic enzyme positioning sites (LEPS), immunoglobulins and polypeptide hormones. The lectin analogy to LEPS and immunoglobulins is exhibited in the lectin-dependent cell and macromolecule lysis for nutritional and homeostatic purposes or for protection, respectively. The hormone-like lectin activity is exhibited in the lectin-dependent cell alterations. In addition to similar functions and effects, the analogy also includes the properties and behavior of these proteins. The suggested hypothesis is based on experimental evidence from microorganisms, plants and animals. It envisions the lectin and lectinoid function in cell attacks on glycosylated molecules or cells, cell-substratum and cell-cell interactions (fusion, invasion, etc.), cell transformation and formation of special structures. All of them according to a developmental program, or special (especially unfavourable) environmental conditions. The lectin resistance to proteolysis and unfavourable pH or temperature is in accord with the suggested hypothesis.

Characteristics of hemolytic and hemagglutinating activities of Treponema denticola

“…The hetnolytic and hemagglutinating activities of T. dentieola were shown to be closely related, with regard to their location, kinetic of production and heat stability. These results tend to support the recent hypothesis of Gilboa-Garber & Garber (6). They suggested that lectin-lysin pairs may reside in the satne molecule or in linked subunits on the cell surface of mieroorganisms.…”

Involvement of caspase activation through release of cytochromecfrom mitochondria in apoptotic cell death of macrophages infected withActinobacillus actinomycetemcomitans

“…The initial event in the pathogenesis of most bacterial infectious diseases is microbial invasion of host cells after the microorganisms adhere to some host tissues, either directly or via some intermediary microorganisms [1]. Actinobacillus actinomycetemcomitans, a periodontopathic bacterium, has been implicated in the pathogenesis of several forms of periodontitis, and extracellular components from the bacterium are known to be potent mediators of its adherence to human oral epithelial cells [2].…”

Comparison of protein patterns in non‐mycorrhizal and vesicular–arbuscular mycorrhizal roots of red clover

“…This interaction may involve Iectins, as in the case of the Rhizobium-legume symbiosis (Diaz et al, 1986). The role of Iectins in this process may be related to the activity of hydrolytic enzymes in that lectin may act as a cofactor which enables key lytic activities (Gilboa-Garber & Garber, 1989). There is evidence that mycorrhizal roots possess higher pectin esterase and endopolymethyl galacturonase activities than non-mycorrhizal roots (Garcia-Romera et al, 1991).…”