The product of uncI gene in F1Fo-ATP synthase operon plays a chaperone-like role to assist c-ring assembly.

Bacterial operons for F(1)F(o)-ATP synthase typically include an uncI gene that encodes a function-unknown small hydrophobic protein. When we expressed a hybrid F(1)F(o) (F(1) from thermophilic Bacillus PS3 and Na(+)-translocating F(o) from Propionigenium modestum) in Escherchia coli cells, we found that uncI derived from P. modestum was indispensable to produce active enzyme; without uncI, c-subunits in F(1)F(o) existed as monomers but not as functional c(11)-ring. When uncI was expressed from another plasmid at the same time, active F(1)F(o) with c(11)-ring was produced. A plasmid containing only uncI and c-subunit gene produced c(11)-ring, but a plasmid containing only c-subunit gene did not. Direct interaction of UncI protein with c-subunits was suggested from copurification of His-tagged UncI protein and c-subunits, both in the state of c(11)-ring and c-monomers. Na(+) induced dissociation of His-tagged UncI protein from c(11)-ring but not from c-monomers. These results show that UncI is a chaperone-like protein that assists c(11)-ring assembly from c-monomers in the membrane.

UncI protein can mediate ring-assembly of c-subunits of FoF1-ATP synthase in vitro.

In F(o)F(1)-ATP synthase, multimeric c-subunits are assembled to a ring (c-ring) in the membranes that rotates as protons flow across F(o). We recently reported that assembly of c-ring of Propionigenium modestum in the membranes of Escherichia coli cells required P. modestum UncI, a product of the conserved uncI gene in the F(o)F(1) operon. However, cooperation with endogenous factors in E. coli remained unclear. Here, P. modestum c-subunit was synthesized in vitro in the presence of liposomes. When c-subunit alone was synthesized, it did not form c-ring. However, when c-subunit and P. modestum UncI were synthesized together, c-ring was formed. Fusion of the two kinds of liposomes, one containing only unassembled c-subunit and the other only UncI, resulted in gradual formation of c-ring. Thus, UncI alone can mediate in vitro post-translational c-ring assembly.

Dual blockade of the rennin-angiotensin system versus maximal recommended dose of angiotensin II receptor blockade in chronic glomerulonephritis.

BACKGROUND: Proteinuria and hypertension are predictors of poor renal outcome in chronic glomerulonephritis (CGN). At the same level of blood pressure (BP) control, we evaluated which is superior, dual blockade of the rennin-angiotensin system (RAS) with both angiotensin-converting enzyme inhibitor (ACEI) and angiotensin II type 1 (AT-1) receptor blockade (ARB) or single blockade of ARB to reduce proteinuria and to preserve renal function in patients with CGN. METHODS: In this prospective, parallel, open study of 86 patients with CGN, we compared the effects on proteinuria and renal functions of 36 months with comparable blood pressure (BP) control achieved by candesartan cilexetil (candesartan, 4-12 mg/day) or benazepril hydrochrolide (benazepril, 2.5-10 mg/day) with candesartan (4 mg/day). Aiming at BP 125/75 mmHg or less, the dose of candesartan (single blockade) or benazepril (dual blockade) was increased. RESULTS: Dual blockade decreased proteinuria more than single blockade with ARB (-42.3 vs. -60.5%, P < 0.01). Renal plasma flow (RPF) and glomerular filtration fraction (GFR) did not change significantly in either group. The filtration fraction (FF) decreased dual blockade more than single blockade (-1.7 vs. -19.0%, P < 0.05). Decreased FF was associated with the reduction of proteinuria (P < 0.05). Six percent of patients with dual blockade were not able to continue the study because of a dry cough. CONCLUSION: Long-term dual blockade decreased proteinuria more than single blockade with ARB. Although ARB and ACEI have a glomerular size-selective function for proteinuria, a greater antiproteinuric effect may depend on renal hemodynamics, especially FF. Increased levels of bradykinin after ACEI can decrease FF and ameliorate proteinuria. Dry cough is a significant adverse effect of ACE inhibitor.

Crystal structure of Ufc1, the Ufm1-conjugating enzyme.

Ubiquitin and ubiquitin-like protein-conjugating enzymes play central roles in posttranslational modification processes. The ubiquitin-fold modifier 1 (Ufm1), one of a variety of ubiquitin-like modifiers, is covalently attached to target proteins via Uba5 and Ufm1-conjugating enzyme 1 (Ufc1), which are analogous to the E1 and E2 ubiquitylation enzymes. As Ufm1-related proteins are conserved in metazoa and plants, the Ufm1 system likely plays important roles in various multicellular organisms. Herein, we report the X-ray structure of human Ufc1 determined at 1.6 A resolution. The Ufc1 structure comprises a canonical E2 domain and an additional N-terminal domain. The Uba5 binding site on Ufc1 was assigned by structural comparison of Ufc1 and Ubc12 and related mutational analyses. In addition, we show that the N-terminal unique domain of Ufc1 contributes to thermal stability.