Binding of uteroglobin to microsomes and plasmatic membranes

Characterization and Cloning of Two Isoforms of Heteroglobin, a Novel Heterodimeric Glycoprotein of the Secretoglobin-Uteroglobin Family Showing Tissue-specific and Sex Differential Expression

“…Contrarily to calcium, it has been shown that lipophilic compounds bind to an internal cavity formed between the two polypeptides of the UGB homodimer (17,27,28), and the existence of such a hydrophobic pocket in heterodimeric SCGBs has also been proposed (10,12). Several groups report UGB binding to cellular and matrix proteins and to a possible membrane receptor (31)(32)(33). Besides reports of different cellular and physiological actions (4,17,21), some of which arise from knock-out projects (34 -36), the physiological role(s) of UGB and, in general, SCGBs is unclear.…”

Calcium‐dependent binding of uteroglobin (PCB‐BP/CCSP) to negatively charged phospholipid liposomes

“…Moreover, PCB-BP/uteroglobin has recently been shown to bind to microsomes and plasmatic membranes. A different mechanism seems involved in this case, as PCB-BP/uteroglobin was associated with binding component(s) with an apparent Mr of 90,000, suggesting the presence of a membrane-associated uteroglobin-binding protein [28]. Nevertheless, it is noteworthy that these experiments were carried out in buffers containing 5 mM calcium.…”

The structural homology between uteroglobin and the pore‐forming domain of colicin A suggests a possible mechanism of action for uteroglobin

“…The crystal structure of the UG-like protein HCClO complexed with phospholipids (Umland et al, 1994) shows that the phospholipid molecule is located in the hydrophobic cavity at the interface between the two monomers. Finally, it has been shown, by direct binding experiments (Gonzalez & Nieto, 1995), that reduced UG binds to microsomes in a nonsaturable fashion, as well as to a specific protein in the microsomal and membrane preparations. Interestingly, myoglobin, which has a clear structural similarity with COLA (Holm & Sander, 1993b;Orengo & Taylor, 1993), has also been shown to be capable of membrane binding in its apo form (Lee & Kim, 1988).…”

“…The proposed membrane binding probably requires a reduction of the two disulfide bonds that join the two monomers. It has indeed been observed that the disulfide bonds of UG had to be reduced in order for it to bind the membrane (Gonzalez & Nieto, 1995).…”

“…For example, a recent series of combined NMR and CD studies (Mammi et al, 1992;Tessari et al, 1993) show that UG peptides interact with membrane. Recently, UG was directly shown to bind to microsomal and membrane preparations (Gonzalez & Nieto, 1995).…”