scholarly journals Insights into the Relationship between Cobamide Synthase and the Cell Membrane

mBio ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Victoria L. Jeter ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Cell Membrane ◽  
Membrane Protein ◽  
Lipid Bilayer ◽  
De Novo ◽  
Integral Membrane Protein ◽  
Phospholipid Bilayer ◽  
Multienzyme Complex ◽  
Coenzyme B ◽  
Lower Ligand

ABSTRACT Cobamides are cobalt-containing cyclic tetrapyrroles used by cells from all domains of life but only produced de novo by some bacteria and archaea. The “late steps” of the adenosylcobamide biosynthetic pathway are responsible for the assembly of the nucleotide loop and are required during de novo synthesis and precursor salvaging. These steps are characterized by activation of the corrin ring and lower ligand base, condensation of the activated precursors to adenosylcobamide phosphate, and removal of the phosphate, yielding a complete adenosylcobamide molecule. The condensation of the activated corrin ring and lower ligand base is performed by an integral membrane protein, cobamide (5′ phosphate) synthase (CobS), and represents an important convergence of two pathways necessary for nucleotide loop assembly. Interestingly, membrane association of this penultimate step is conserved among all cobamide producers, yet the physiological relevance of this association is not known. Here, we present the purification and biochemical characterization of the CobS enzyme of the enterobacterium Salmonella enterica subsp. enterica serovar Typhimurium strain LT2, investigate its association with liposomes, and quantify the effect of the lipid bilayer on its enzymatic activity and substrate affinity. We report a purification scheme that yields pure CobS protein, allowing in vitro functional analysis. Additionally, we report a method for liposome reconstitution of CobS, allowing for physiologically relevant studies of this inner membrane protein in a phospholipid bilayer. In vitro and in vivo data reported here expand our understanding of CobS and the implications of membrane-associated adenosylcobamide biosynthesis. IMPORTANCE Salmonella is a human pathogen of worldwide importance, and coenzyme B12 is critical for the pathogenic lifestyle of this bacterium. The importance of the work reported here lies on the improvements to the methodology used to isolate cobamide synthase, a polytopic integral membrane protein that catalyzes the penultimate step of coenzyme B12 biosynthesis. This advance is an important step in the analysis of the proposed multienzyme complex responsible for the assembly of the nucleotide loop during de novo coenzyme B12 biosynthesis and for the assimilation of incomplete corrinoids from the environment. We proposed that cobamide synthase is likely localized to the cell membrane of every coenzyme B12-producing bacterium and archaeum sequenced to date. The new knowledge of cobamide synthase advances our understanding of the functionality of the enzyme in the context of the lipid bilayer and sets the foundation for the functional-structural analysis of the aforementioned multienzyme complex.

scholarly journals The CbiB Protein of Salmonella enterica Is an Integral Membrane Protein Involved in the Last Step of the De Novo Corrin Ring Biosynthetic Pathway

2007 ◽  
Vol 189 (21) ◽  
pp. 7697-7708 ◽  
Author(s):  
Carmen L. Zayas ◽  
Kathy Claas ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Membrane Protein ◽  
Salmonella Enterica ◽  
De Novo ◽  
Integral Membrane Protein ◽  
In Vivo Studies ◽  
Single Amino Acid ◽  
Serovar Typhimurium ◽  
Ethanolamine Phosphate ◽  
Coenzyme B

ABSTRACT We report results of studies of the conversion of adenosylcobyric acid (AdoCby) to adenosylcobinamide-phosphate, the last step of the de novo corrin ring biosynthetic branch of the adenosylcobalamin (coenzyme B12) pathway of Salmonella enterica serovar Typhimurium LT2. Previous reports have implicated the CbiB protein in this step of the pathway. Hydropathy analysis predicted that CbiB would be an integral membrane protein. We used a computer-generated topology model of the primary sequence of CbiB to guide the construction of CbiB-LacZ and CbiB-PhoA protein fusions, which were used to explore the general topology of CbiB in the cell membrane. A refined model of CbiB as an integral membrane protein is presented. In vivo analyses of the effect of single-amino-acid changes showed that periplasm- and cytosol-exposed residues are critical for CbiB function. Results of in vivo studies also show that ethanolamine-phosphate (EA-P) is a substrate of CbiB, but l-Thr-P is not, and that CbiB likely activates AdoCby by phosphorylation. The latter observation leads us to suggest that CbiB is a synthetase not a synthase enzyme. Results from mass spectrometry and bioassay experiments indicate that serovar Typhimurium synthesizes norcobalamin (cobalamin lacking the methyl group at C176) when EA-P is the substrate of CbiB.

scholarly journals Cytosolic protein binding to band-3 protein inhibits endocytosis of isolated human erythrocyte membranes

1982 ◽  
Vol 207 (3) ◽  
pp. 595-598 ◽  
Author(s):  
K A Cordes ◽  
J M Salhany
Keyword(s):  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Band 3 ◽  
Erythrocyte Membranes ◽  
Band 3 Protein ◽  
High Affinity ◽  
Human Erythrocyte Membranes ◽  
Affinity Interaction ◽  
Cytoplasmic Side

Recent studies of haemoglobin binding to the cytoplasmic side of the erythrocyte membrane have shown that the predominant high-affinity interaction occurs with the major integral membrane protein known as band-3 protein and that this interaction may occur within the intact erythrocyte in a manner regulated by cell pH. We report here that haemoglobin and glyceraldehyde 3-phosphate dehydrogenase binding to band-3 protein in isolated membranes can inhibit endocytosis during vesiculation in vitro. The specificity of this effect was demonstrated by showing that myoglobin, which has an affinity for the membrane fully one to two orders of magnitude lower than that for haemoglobin, does not inhibit endocytosis.

scholarly journals The synthesis of murine ferrochelatase in vitro and in vivo

1988 ◽  
Vol 254 (3) ◽  
pp. 799-803 ◽  
Author(s):  
S R Karr ◽  
H A Dailey
Keyword(s):  
Membrane Protein ◽  
Biosynthetic Pathway ◽  
Integral Membrane Protein ◽  
Mitochondrial Proteins ◽  
Isolated Mitochondria ◽  
Mitochondrial Inner Membrane ◽  
Carbonyl Cyanide ◽  
A Cell

Ferrochelatase (protohaem ferro-lyase, EC 4.99.1.1), the terminal enzyme of the haem-biosynthetic pathway, is an integral membrane protein of the mitochondrial inner membrane. When murine erythroleukaemia cells are labelled in vivo with [35S]methionine, lysed, and the extract is immunoprecipitated with rabbit anti-(mouse ferrochelatase) antibody, a protein of Mr 40,000 is isolated. However, when isolated mouse RNA is translated in a cell-free reticulocyte extract, a protein of Mr 43,000 is isolated. Incubation of this Mr 43,000 protein with isolated mitochondria resulted in processing of the Mr 43,000 precursor to the Mr 40,000 mature-sized protein. Addition of carbonyl cyanide m-chlorophenylhydrazone and/or phenanthroline inhibits this processing. These data indicate that ferrochelatase, like most mitochondrial proteins, is synthesized in the cytoplasm as a larger precursor and is then translocated and processed to a mature-sized protein in an energy-required step.

scholarly journals Import of a 22-kDa peroxisomal integral membrane protein into peroxisomes in vitro.

1989 ◽  
Vol 53 (2) ◽  
pp. 591-592 ◽  
Author(s):  
Yukio FUJIKI ◽  
Izumi KASUYA ◽  
Hitoshi MORI
Keyword(s):  
Membrane Protein ◽  
Integral Membrane Protein

scholarly journals Structure, biosynthesis, and localization of dipeptidyl aminopeptidase B, an integral membrane glycoprotein of the yeast vacuole.

1989 ◽  
Vol 108 (4) ◽  
pp. 1363-1373 ◽  
Author(s):  
C J Roberts ◽  
G Pohlig ◽  
J H Rothman ◽  
T H Stevens
Keyword(s):  
Membrane Protein ◽  
Secretory Pathway ◽  
Apparent Molecular Weight ◽  
Integral Membrane Protein ◽  
Restrictive Temperature ◽  
Proteolytic Activation ◽  
Hydrophobic Domain ◽  
Yeast Vacuole ◽  
Dipeptidyl Aminopeptidase

We have characterized the structure, biogenesis, and localization of dipeptidyl aminopeptidase B (DPAP B), a membrane protein of the yeast vacuole. An antibody specific for DPAP B recognizes a 120-kD glycoprotein in yeast that behaves like an integral membrane protein in that it is not removed from membranes by high pH Na2CO3 treatment. Inspection of the deduced amino acid sequence of DPAP B reveals a hydrophobic domain near the NH2 terminus that could potentially span a lipid bilayer. The in vitro enzymatic activity and apparent molecular weight of DPAP B are unaffected by the allelic state of PEP4, a gene essential for the proteolytic activation of a number of soluble vacuolar hydrolases. DPAP B is synthesized as a glycosylated precursor that is converted to the mature 120-kD species by carbohydrate addition. The precursor form of DPAP B accumulates in sec mutants (Novick, P., C. Field, and R. Schekman. 1980. Cell. 21:205-215) that are blocked at the ER (sec18) or Golgi apparatus (sec7), but not at secretory vesicles (sec1). Immunolocalization of DPAP B in wild-type or sec1 mutant cells shows that the protein resides in the vacuolar membrane. However, it is present in non-vacuolar compartments in sec18 and sec7 cells, confirming that the delivery of DPAP B is blocked in these mutants. Interestingly, DPAP B appears to stain the nuclear envelope in a sec18 mutant, which is consistent with the accumulation of DPAP B in the ER membrane at the restrictive temperature. These results suggest that soluble and membrane-bound vacuolar proteins use the same stages of the secretory pathway for their transport.

scholarly journals Amino acid permeases require COPII components and the ER resident membrane protein Shr3p for packaging into transport vesicles in vitro.

1996 ◽  
Vol 135 (3) ◽  
pp. 585-595 ◽  
Author(s):  
M J Kuehn ◽  
R Schekman ◽  
P O Ljungdahl
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Plasma Membrane Atpase ◽  
Amino Acid Permease ◽  
Transport Vesicles ◽  
Amino Acid Permeases ◽  
Histidine Permease

In S. cerevisiae lacking SHR3, amino acid permeases specifically accumulate in membranes of the endoplasmic reticulum (ER) and fail to be transported to the plasma membrane. We examined the requirements of transport of the permeases from the ER to the Golgi in vitro. Addition of soluble COPII components (Sec23/24p, Sec13/31p, and Sar1p) to yeast membrane preparations generated vesicles containing the general amino acid permease. Gap1p, and the histidine permease, Hip1p. Shr3p was required for the packaging of Gap1p and Hip1p but was not itself incorporated into transport vesicles. In contrast, the packaging of the plasma membrane ATPase, Pma1p, and the soluble yeast pheromone precursor, glycosylated pro alpha factor, was independent of Shr3p. In addition, we show that integral membrane and soluble cargo colocalize in transport vesicles, indicating that different types of cargo are not segregated at an early step in secretion. Our data suggest that specific ancillary proteins in the ER membrane recruit subsets of integral membrane protein cargo into COPII transport vesicles.

scholarly journals Transmembrane topology of the mammalian KDEL receptor.

1993 ◽  
Vol 13 (10) ◽  
pp. 6435-6441 ◽  
Author(s):  
P Singh ◽  
B L Tang ◽  
S H Wong ◽  
W Hong
Keyword(s):  
Membrane Protein ◽  
Fusion Proteins ◽  
Integral Membrane Protein ◽  
In Vitro Translation ◽  
Translation System ◽  
Transmembrane Topology ◽  
Amino Terminal ◽  
Hydrophilic Region ◽  
Kdel Receptor

The mammalian KDEL receptor is an integral membrane protein with seven hydrophobic regions. Fusion proteins comprising a 37-kDa N-glycosylation reporter fused downstream of amino-terminal fragments of the KDEL receptor with varying numbers of hydrophobic regions were synthesized in an in vitro translation system containing canine pancreatic microsomes. The luminal or cytosolic orientation of the reporter, and hence of the hydrophilic region to which it is fused, was inferred from the presence or absence of glycosylation, which occurs only in the lumen of the microsomes. The cytosolic orientation of the N and C termini was also confirmed immunocytochemically. Our results suggest that the KDEL receptor is inserted into the membrane with only six transmembrane domains and that both the amino and carboxy termini are located in the cytoplasm.

scholarly journals YidC Occupies the Lateral Gate of the SecYEG Translocon and Is Sequentially Displaced by a Nascent Membrane Protein

2013 ◽  
Vol 288 (23) ◽  
pp. 16295-16307 ◽  
Author(s):  
Ilie Sachelaru ◽  
Narcis Adrian Petriman ◽  
Renuka Kudva ◽  
Patrick Kuhn ◽  
Thomas Welte ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Lipid Bilayer ◽  
Transmembrane Domains ◽  
Cross Linking ◽  
Lipid Phase ◽  
Lipid Transfer ◽  
Lateral Gate

Most membrane proteins are co-translationally inserted into the lipid bilayer via the universally conserved SecY complex and they access the lipid phase presumably via a lateral gate in SecY. In bacteria, the lipid transfer of membrane proteins from the SecY channel is assisted by the SecY-associated protein YidC, but details on the SecY-YidC interaction are unknown. By employing an in vivo and in vitro site-directed cross-linking approach, we have mapped the SecY-YidC interface and found YidC in contact with all four transmembrane domains of the lateral gate. This interaction did not require the SecDFYajC complex and was not influenced by SecA binding to SecY. In contrast, ribosomes dissociated the YidC contacts to lateral gate helices 2b and 8. The major contact between YidC and the lateral gate was lost in the presence of ribosome nascent chains and new SecY-YidC contacts appeared. These data demonstrate that the SecY-YidC interaction is influenced by nascent-membrane-induced lateral gate movements.

Sign in / Sign up

Export Citation Format

Share Document