Serum allotypes in ovarian follicular fluids of pigs

Summary. Sera and ovarian follicular fluids of 158 sows were tested with 27 allotype reagents. Immunodiffusion in agar gel (microtest) and haemagglutination inhibition were used as detection methods.
Out of eight 'individual' (Lpb 1,-2,-3,-4,-5,-6,-7,-9) and four 'common' (Lpb 12,-13,-14,-16) specificities of serum beta-lipoproteins (LDL), 11 were present in sera, but none in follicular fluids. On the other hand, Lpr 1 and Lpr (x) allotypes of the VHDL + VLDL beta-lipoprotein system were detected both in sera and in follicular fluids. Of four antigens of the Gp system (Gp A,-a, -B,-b), only the 'dominant' characters, Gp A and Gp B, occurred in the follicular fluid. The typing of polymorphic IgG immunoglobulins (IgG-a or IgG-b system) showed that B1 or A2, B2 or A1 and B3 or A(x) allotypes could be detected both in serum and follicular fluid. Among allotypes that were not yet genetically classified, only the P3 specificity was not found in the population tested. The G1 allotype (preliminarily described as an alpha-globulin) was present in sera only, and the remaining allotypes, G9, P1, P16 and P23 (alpha- or beta-globulins) were present both in sera and follicular fluids.
The mechanism of the transmission of serum proteins into ovarian follicles and their possible importance is discussed.     

Serum allotypes in ovarian follicular fluids of pigs

Sera and ovarian follicular fluids of 158 sows were tested with 27 allotype reagents. Immunodiffusion in agar gel (microtest) and haemagglutination inhibition were used as detection methods. Out of eight 'individual' (Lpb 1,-2,-3,-4,-5,-6,-7,-9) and four 'common' (Lpb 12,-13,-14,-16) specificities of serum beta-lipoproteins (LDL), 11 were present in sera, but none in follicular fluids. On the other hand, Lpr 1 and Lpr (x) allotypes of the VHDL + VLDL beta-lipoprotein system were detected both in sera and in follicular fluids. Of four antigens of the Gp system (Gp A,-a, -B,-b), only the 'dominant' characters, Gp A and Gp B, occurred in the follicular fluid. The typing of polymorphic IgG immunoglobulins (IgG-a or IgG-b system) showed that B1 or A2, B2 or A1 and B3 or A(x) allotypes could be detected both in serum and follicular fluid. Among allotypes that were not yet genetically classified, only the P3 specificity was not found in the population tested. The G1 allotype (preliminarily described as an alpha-globulin) was present in sera only, and the remaining allotypes, G9, P1, P16 and P23 (alpha- or beta-globulins) were present both in sera and follicular fluids. The mechanism of the transmission of serum proteins into ovarian follicles and their possible importance is discussed.     

Gm typing by immunoglobulin heavy-chain gene RFLP analysis.

This study was undertaken to investigate a means of assigning Gm allotypes to Caucasians by RFLP analysis. A single immunoglobulin heavy-chain gamma-4 cDNA probe (HU gamma 4) was hybridized with genomic DNA digested separately with two restriction enzymes, TaqI and PvuII. Results showed excellent correlation (P less than .001) between serologically defined Gm allotypes G1m(1), G1m(2), G2m(23), and G1m;G3m (3;5,10) and RFLPs identified with the (HU gamma 4) probe. We conclude that it is now possible to define common Gm haplotypes in Caucasians by RFLP analysis. This method provides a useful adjunct to serological allotyping and indeed has several important advantages over traditional serology: it allows confident Gm assignment and the definition of homozygous and heterozygous Gm arrangements, is highly reproducible, and is readily executed in any molecular genetic laboratory.     

A2G--a new system of alpha-2-globulin allotypes in pig blood serum]

Combinations of four alpha-2-globulin allotypes were studied for their distribution in pigs of nine different breeds and hybrid groups. Based on this analysis, a new, previously unpublished polyallelic genetic system designated A2G was postulated. The complex alleles of this system control alpha-2-globulin allotypes and are suggested to be encoded by genes of two subloci. One of these subloci is virtually monomorphic, whereas the other has at least four allelic variants.     

A2G Is a New System of α-2-Globulin Allotypes in Pig Blood Serum

Combinations of four -2-globulin allotypes were studied for their distribution in pigs of nine different breeds and hybrid groups. Based on this analysis, a new, previously unpublished polyallelic genetic system designated A2G was postulated. The complex alleles of this system control -2-globulin allotypes and are suggested to be encoded by genes of two subloci. One of these subloci is virtually monomorphic, whereas the other has at least four allelic variants.     

Interaction between T cell receptor beta chain and immunoglobulin heavy chain region genes in susceptibility to insulin-dependent diabetes mellitus.

Despite some reports of an association between insulin-dependent diabetes mellitus (IDDM) and a BglII RFLP in the T cell receptor beta chain (TCRB) constant region, results of several recent studies, including our own, have failed to support such an association. However, we here report evidence for an IDDM-TCRB relationship which is dependent on immunoglobulin heavy-chain-region genes. We analyzed 198 unrelated diabetics and 84 normal siblings (maximum one sibling per diabetic) typed for the BglII TCRB RFLP and Gm immunoglobulin allotypes Glm(1), Glm(2), G2m(23), and G3m(5), which identify the four common Gm haplotypes. The BglIII TCRB genotype frequencies were significantly different between diabetics positive and negative for G2m(23) (P = .017) and G3m(5) (P = .021) but were not different between normal siblings positive and negative for those allotypes (P = .94 and P = .77, respectively). Thus, there were significant interactions between TCRB, Gm, and IDDM for two of the four immunoglobulin allotypes examined. We have previously reported interactions between HLA, Gm (particularly G2m(23)), and IDDM and postulate that the TCRB-Gm-IDDM and HLA-Gm-IDDM interaction effects may be functionally related.     

G6PC3 mutations are associated with a major defect of glycosylation: a novel mechanism for neutrophil dysfunction

Glucose-6-phosphatase, an enzyme localized in the endoplasmic reticulum (ER), catalyzes the hydrolysis of glucose-6-phosphate (G6P) to glucose and inorganic phosphate. In humans, there are three differentially expressed glucose-6-phosphatase catabolic genes (G6PC1-3). Recently, it has been shown that mutations in the G6PC3 gene result in a syndrome associating congenital neutropenia and various organ malformations. The enzymatic function of G6PC3 is dependent on G6P transport into the ER, mediated by G6P translocase (G6PT). Mutations in the gene encoding G6PT result in glycogen storage disease type-1b (GSD-1b). Interestingly, GSD-1b patients exhibit a similar neutrophil dysfunction to that observed in G6PC3-deficient patients. To better understand the causes of neutrophil dysfunction in both diseases, we have studied the neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase of patients with G6PC3 and G6PT syndromes. Unexpectedly, sodium dodecyl sulfate-polyacrylamide gel electrophoresis experiments indicated hypo-glycosylation of gp91(phox), the electron-transporting component of the NADPH oxidase, in all of these patients. Rigorous mass spectrometric glycomic profiling showed that most of the complex-type antennae which characterize the neutrophil N-glycome of healthy individuals were severely truncated in the patients' neutrophils. A comparable truncation of the core 2 antenna of the O-glycans was also observed. This aberrant neutrophil glycosylation is predicted to have profound effects on the neutrophil function and merit designation of both syndromes as a new class of congenital disorders of glycosylation.     

3 new allotypes of mink blood serum alpha2-lipoproteins--Lpm 6, Lpm 7, Lpm 8]

Three new allotypes were discovered in mink sera by means of isoimmunization. Based on the results of identifications, they were referred to the Lpm system of serum alpha2-lipoprotein. They were designated as Lpm 6, Lpm 7 and Lpm 8. The allotyping of serum samples from 342 minks made possible to establish a relation between Lpm 7 and Lpm 8 using the chi2 method; it was also found that these two allotypes related to each of the first five Lpm as well as to their phenotypes, which was described earlier. There was a significant dependence of the expression of Lpm 6 on Lpm 5 indicating a genetic relation between Lpm 6 and other allotypes. The detection of Lpm 6, 7 and 8, which are the most likely under the control of the same gene (or a sustem of genes) as Lpm 1, 2, 3 and 5, is an evidence for the complex structure of the Lpm locus.     

Homology between the Lpm system of allotypes in the American mink and the Gp system of allotypes in the domestic pig]

The 5 alpha-macroglobulin allotypes alpha M1, alpha M2, alpha M3, alpha M4 and alpha M5 were identified in pig. The alpha M1 allotype was reported as a marker of pig alpha-macroglobulin, the latter being homologous to alpha 2-macroglobulins in human and in mink. The allotypes alpha M2-alpha M5 were specified as markers of the second isotypical variant of pig alpha-macroglobulins, which was homologous to mink Lpm macroglobulin (alpha 1M). As seen from data obtained by International Comparative Test ISABR 87-88, alpha M1 is a new allotype, while allotypes alpha M2--alpha M5 correspond to four allotypes in the Gp system (Janik et al.). Based on these data, a conclusion was made on the homology between the Lpm system in american mink and the Gp system in pig. Since the allotypes studied are the part of alpha-macroglobulins, a locus controlling them was designated the AM locus. We also find it more advantageous to apply the same name to the homologous locus in mink, instead of the Lpm used earlier. Genetic control of 5 allotypes was studied and the structure of the AM locus in pig analysed in detail. Comparative study of organization of the above locus and the homologous locus in mink was carried out.     

Surprising negative association between IgG1 allotype disparity and anti-adalimumab formation: a cohort study

Introduction

The human monoclonal antibody adalimumab is known to induce an anti-globulin response in some adalimumab-treated patients. Antibodies against adalimumab (AAA) are associated with non-response to treatment. Immunoglobulins, such as adalimumab, carry allotypes which represent slight differences in the amino acid sequences of the constant chains of an IgG molecule. Immunoglobulins with particular IgG (Gm) allotypes are racially distributed and could be immunogenic for individuals who do not express these allotypes. Therefore, we investigated whether a mismatch in IgG allotypes between adalimumab and IgG in adalimumab-treated patients is associated with the development of AAA.

Methods

This cohort study consisted of 250 adalimumab-treated rheumatoid arthritis (RA) patients. IgG allotypes were determined for adalimumab and for all patients. Anti-idiotype antibodies against adalimumab were measured with a regular radio immunoassay (RIA), and a newly developed bridging enzyme linked immunosorbent assay (ELISA) was used to measure anti-allotype antibodies against adalimumab. The association between AAA and the G1m3 and the G1m17 allotypes was determined. For differences between groups we used the independent or paired samples t-test, Mann-Whitney test or Chi square/Fisher's exact test as appropriate. To investigate the influence of confounders on the presence or absence of AAA a multiple logistic regression-analysis was used.

Results

Adalimumab carries the G1m17 allotype. No anti-allotype antibodies against adalimumab were detected. Thirty-nine out of 249 patients had anti-idiotype antibodies against adalimumab (16%). IgG allotypes of RA patients were associated with the frequency of AAA: patients homozygous for G1m17 had the highest frequency of AAA (41%), patients homozygous for G1m3 the lowest frequency (10%), and heterozygous patients' AAA frequency was 14% (P = 0.0001).

Conclusions

An allotype mismatch between adalimumab and IgG in adalimumab-treated patients did not lead to a higher frequency of AAA. On the contrary, patients who carried the same IgG allotype as present on the adalimumab IgG molecule, had the highest frequency of anti-adalimumab antibodies compared to patients whose IgG allotype differed from adalimumab. This suggests that the allotype of adalimumab may not be highly immunogenic. Furthermore, patients carrying the G1m17-allotype might be more prone to antibody responses.     

Group A Rotavirus in Sewage Samples from Barcelona and Cairo: Emergence of Unusual Genotypes

The presence of rotavirus strains in sewage samples from Cairo, Egypt (November 1998 to October 1999), and Barcelona, Spain (November 1998 to December 2002), was investigated by using a generic molecular detection method based on amplification of a VP6 gene fragment. Overall, 85.7 and 66.9% of the sewage samples from Cairo and Barcelona, respectively, were positive. Positive samples were characterized further, and VP7 and VP4 genotypes were determined. Although 30% of the positive samples from Cairo were G untypeable, the distribution of G types in the positive samples was 69.6% G1, 13% G3, 8.7% G4, and 8.7% G9. The percentage of untypeable samples was much higher for the Barcelona samples (56.5%), and the distribution in the positive samples was 56.4% G1, 31.5% G3, 6% G9, 4% G2, and 2% G5. When the P types were examined, 26.7% of the positive samples from Cairo were untypeable, and the distribution of types in the positive samples was 53.3% P[8], 30% P[6], and 16.6% P[4]. In Barcelona, 27.2% of the samples were P untypeable, and the frequencies of the types detected were 49.7% P[8], 37.2% P[4], 8.8% P[6], and 4.2% P[9]. The distribution for strains from Cairo was 38.5% P[8]G1, 27% P[6]G1, 11.5% P[4]G1, 11.5% P[8]G3, 7.7% P[6]G4, and 3.8% P[8]G9. Strikingly, equivalent frequencies of common and uncommon strains were observed for Barcelona samples, and the distribution was 38.8% P[8]G1, 30.6% P[4]G1, 11.6% P[8]G3, 6.6% P[4]G3, 5.8% P[6]G1, 1.6% P[6]G3, 1.6% P[9]G1, 0.8% P[4]G2, 0.8% P[6]G9, 0.8% P[8]G9, and 0.8% P[8]G5. Additionally, two P[−]G5 strains were isolated in Barcelona, and the porcine or human origin of these strains was unclear. Rotavirus variability exhibited not only a geographic pattern but also a temporal pattern.     

Group A rotavirus in sewage samples from Barcelona and Cairo: emergence of unusual genotypes

The presence of rotavirus strains in sewage samples from Cairo, Egypt (November 1998 to October 1999), and Barcelona, Spain (November 1998 to December 2002), was investigated by using a generic molecular detection method based on amplification of a VP6 gene fragment. Overall, 85.7 and 66.9% of the sewage samples from Cairo and Barcelona, respectively, were positive. Positive samples were characterized further, and VP7 and VP4 genotypes were determined. Although 30% of the positive samples from Cairo were G untypeable, the distribution of G types in the positive samples was 69.6% G1, 13% G3, 8.7% G4, and 8.7% G9. The percentage of untypeable samples was much higher for the Barcelona samples (56.5%), and the distribution in the positive samples was 56.4% G1, 31.5% G3, 6% G9, 4% G2, and 2% G5. When the P types were examined, 26.7% of the positive samples from Cairo were untypeable, and the distribution of types in the positive samples was 53.3% P[8], 30% P[6], and 16.6% P[4]. In Barcelona, 27.2% of the samples were P untypeable, and the frequencies of the types detected were 49.7% P[8], 37.2% P[4], 8.8% P[6], and 4.2% P[9]. The distribution for strains from Cairo was 38.5% P[8]G1, 27% P[6]G1, 11.5% P[4]G1, 11.5% P[8]G3, 7.7% P[6]G4, and 3.8% P[8]G9. Strikingly, equivalent frequencies of common and uncommon strains were observed for Barcelona samples, and the distribution was 38.8% P[8]G1, 30.6% P[4]G1, 11.6% P[8]G3, 6.6% P[4]G3, 5.8% P[6]G1, 1.6% P[6]G3, 1.6% P[9]G1, 0.8% P[4]G2, 0.8% P[6]G9, 0.8% P[8]G9, and 0.8% P[8]G5. Additionally, two P[-]G5 strains were isolated in Barcelona, and the porcine or human origin of these strains was unclear. Rotavirus variability exhibited not only a geographic pattern but also a temporal pattern.     

Dynamics of Inter-heavy Chain Interactions in Human Immunoglobulin G (IgG) Subclasses Studied by Kinetic Fab Arm Exchange

Interdomain interactions between the CH3 domains of antibody heavy chains are the first step in antibody assembly and are of prime importance for maintaining the native structure of IgG. For human IgG4 it was shown that CH3-CH3 interactions are weak, resulting in the potential for half-molecule exchange (“Fab arm exchange”). Here we systematically investigated non-covalent interchain interactions for CH3 domains in the other human subclasses, including polymorphisms (allotypes), using real-time monitoring of Fab arm exchange with a FRET-based kinetic assay. We identified structural variation between human IgG subclasses and allotypes at three amino acid positions (Lys/Asn-392, Val/Met-397, Lys/Arg-409) to alter the strength of inter-domain interactions by >6 orders of magnitude. Each substitution affected the interactions independent from the other substitutions in terms of affinity, but the enthalpic and entropic contributions were non-additive, suggesting a complex interplay. Allotypic variation in IgG3 resulted in widely different CH3 interaction strengths that were even weaker for IgG3 than for IgG4 in the case of allotype G3m(c3c5*/6,24*), whereas G3m(s*/15*) was equally stable to IgG1. These interactions are sufficiently strong to maintain the structural integrity of IgG1 during its normal life span; for IgG2 and IgG3 the inter-heavy chain disulfide bonds are essential to prevent half-molecule dissociation, whereas the labile hinge disulfide bonds favor half-molecule exchange in vivo for IgG4.     

The results of international comparative testing of reagents to swine serum protein allotypes conducted in 1987-1988

Antisera to 15 allotypes of pig serum protein were raised and compared with those prepared elsewhere, within the framework of International Comparison Test of pig blood groups and polymorphic proteins and enzymes in 1987-1988. Of 15 allotypes tested 8 were found to coincide with the known GpB, GpD, GpA, Gpa, IGH3 C1, Lpb3, Lpb12, Lbr1. For 7 allotypes left, no analogues were found out. They seem very likely to be new allotypes of pig serum proteins.     

Evidence that NADPH is the actual substrate of the oxidase responsible for the "respiratory burst" of phagocytosing polymorphonuclear leukocytes

The relationship between glucose metabolism and the "respiratory burst" of phagocytosing polymorphonuclear leukocytes (PMN) was studied in a Renex 30-treated cell system of guinea pig PMN by a polarometric technique. Phagocytosing PMN were treated with a detergent (Renex 30) and recovery of respiratory activity was examined by addition of various concentrations of NADP and glucose-6-phosphate (G6P) to determine the availability of endogenously formed NADPH via the hexose monophosphate (HMP) pathway. The oxygen uptake by phagocytosing PMN ceased after the treatment with Renex 30 and was restored by the addition of NADP and G6P. Furthermore, the restoration of oxygen uptake was linearly proportional to the rate of NADPH formation on increase in either NADP or G6P concentration. Resting PMN showed no respiratory activity even in the presence of excess NADP and G6P, in which NADPH was formed at the same rate as in phagocytosing PMN. In a parallel experiment, recovery of respiratory activity was examined in the same system by addition of NAD and glyceraldehyde-3-phosphate (G3P) in that order to clarify whether the respiratory enzyme can utilize NADH formed via the glycolytic pathway. In contrast to the results in the NADPH-forming system, the addition of NAD and G3P induced slight oxygen uptake of Renex 30-treated PMN, but there was no difference in the oxygen uptake between resting and phagocytosis-activated PMN. The results indicated that the primary oxidase responsible for the "respiratory burst" is NADPH oxidase, and that its activity is coupled with glucose oxidation via the HMP pathway without the participation of other metabolic pathways such as glycolysis.     

Evolution of the rabbit immunoglobulin κ chain genes

We have analyzed the organization and the structure of rabbit chain genes encoding b allotypes in wild rabbits. The 1 gene of the b95 allotype was cloned and its structure determined. The J region is composed of five segments but only J2 appears to be functional and is identical to the J2 segment of the b4 allotype. The J region is highly conserved among the various b allotypes, whereas the constant region exon displays a high level of differences when compared with other allotypes (9%–30% of different amino acids). The b95 J region is closer to that of b4^var and the constant region to b5 allotype constant region. Alignment of nucleotide sequences revealed that the constant region exon displays segmental similarities with b4 and bas constant regions. The mosaic structure of b95 allotype gene indicates that complex allotypes of 1 genes may result from genetic exchanges of gene conversion between the different genes.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide database and have been assigned the accession number M22542. Address correspondence and offprint requests to: P.-A. Cazenave.     

BamHI-SacI RFLP and Gm analysis of the immunoglobulin IGHG genes in the Northern Selkups (west Siberia): new haplotypes with deletion, duplication and triplication

Gm immunoglobulin allotypes have been studied in 1157 individuals of seven Northern Selkup populations, which account for 80% of the entire population of this west Siberian tribe. This study confirms that the northern Selkup populations are a Caucasoid-Mongoloid hybrid. Restriction fragment length polymorphism (RFLP) analysis of the IGHG genes using double BamHI-SacI digests, performed on 475 DNA samples, allowed us to describe nine new BamHI-SacI haplotypes (BS47 to BS55), eight of them being characterized by IGHG gene deletion or duplication: G1 (BS49) or G4 (BS55) deletion, G4 duplication (BS51), GP-G2-G4 multigene deletion (BS50), duplication (BS48, BS53 and BS54) or triplication (BS52). A new rare Gm haplotype 15,16*;1,17;23 has been found associated with BS52. The BS51 haplotype characterized by a duplicated G4 gene (additional 7.85 kb G4 band identifying a new G4*C5 allele) was always found associated with the Gm 5*;3;23 haplotype. A high RFLP diversity has been observed for the Northern-Mongoloid haplotype Gm 15,16*;1,17;.. which was found (1) with the BS27 haplotype characterized by a 3-exon hinge G3 gene, (2) with two different GP-G2-G4 multigene duplications, BS53 and BS54 haplotypes, which differ by the size of the duplicated G4 genes, and (3) with the BS55 haplotype characterized by a G4 deletion. In the Northern Selkups, haplotypes with duplicated genes were observed at a higher frequency (24%) than haplotypes with deleted genes (6%).     

Microbial nanowires: type IV pili or cytochrome filaments?

A dynamic field of study has emerged involving long-range electron transport by extracellular filaments in anaerobic bacteria, with Geobacter sulfurreducens being used as a model system. The interest in this topic stems from the potential uses of such systems in bioremediation, energy generation, and new bio-based nanotechnology for electronic devices. These conductive extracellular filaments were originally thought, based upon low-resolution observations of dried samples, to be type IV pili (T4P). However, the recently published atomic structure for the T4P from G. sulfurreducens, obtained by cryo-electron microscopy (cryo-EM), is incompatible with the numerous models that have been put forward for electron conduction. As with all high-resolution structures of T4P, the G. sulfurreducens T4P structure shows a partial melting of the α-helix that substantially impacts the aromatic residue positions such that they are incompatible with conductivity. Furthermore, new work using high-resolution cryo-EM shows that conductive filaments thought to be T4P are actually polymerized cytochromes, with stacked heme groups forming a continuous conductive wire, or extracellular DNA. Recent atomic structures of three different cytochrome filaments from G. sulfurreducens suggest that such polymers evolved independently on multiple occasions. The expectation is that such polymerized cytochromes may be found emanating from other anaerobic organisms.     

Solution structure of a tRNA with a large variable region: yeast tRNASer

Different chemical reagents were used to study the tertiary structure of yeast tRNASer, a tRNA with a large variable region: ethylnitrosourea, which alkylates the phosphate groups; dimethylsulphate, which methylates N-7 of guanosine and N-3 of cytosine; and diethylpyrocarbonate, which modifies N-7 of adenine. The non-reactivity of N-3 of cytidine 47:1, 47:6, 47:7 and 47:8 and the reactivity of cytidine 47:3 confirms the existence of a variable stem of four base-pairs and a short variable loop of three residues. For the N-7 positions in purines, accessible residues are G1, G10, Gm18, G19, G30, I34, G35, A36, i6A37, G45, G47, G47:5, G47:9 and G73. The protection of N-7 atoms of residues G9, G15, A21, A22 and G47:9 reflects the tertiary folding. Strong phosphate protection was observed for P8 to P11, P20:1 to P22, P48 to P50 and for P59 and P60. A model was built on a PS300 graphic system on the basis of these data and its stereochemistry refined. While trying to keep most tertiary interactions, we adapted the tertiary folding of the known structures of tRNAAsp and tRNAPhe to the present sequence and solution data. The resulting model has the variable arm not far from the plane of the common L-shaped structure. A generalization of this model to other tRNAs with large variable regions is discussed.     

Compartmentation in the induction of the hexose-6-phosphate transport system of Escherichia coli

The induction of the hexose-6-phosphate transport system was investigated. Glucose-6-phosphate (G6P) at concentrations as low as 10(-4)m was able to induce this system in wild-type cells, as well as in mutants lacking phosphoglucose isomerase or G6P dehydrogenase. Growth in the presence of fructose-6-phosphate (F6P) induced the system only if the cells contained phosphoglucose isomerase. Furthermore, glucose and F6P were found to induce the system only if the extracellular concentration of G6P became appreciable in the medium as a consequence of the leakage of intracellular G6P formed from the glucose or F6P. Intracellular G6P was not an inducer even at high concentrations. The metabolism of glucose inhibited the induction of the hexose-6-phosphate transport system. Hypotheses for this compartmentalization of inducer and membrane-associated induction are presented.