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Biomedical subjects

P Lin

Publications and source records attributed to P Lin.

At least 73 records · Page 4Linked to original sources
PubMed1998

DNA content and other factors associated with ten-year survival after resection of pancreatic carcinoma.

BACKGROUND AND OBJECTIVES: The 5-year survival rates after resection of pancreatic carcinoma have recently increased and are predicted by tumor size, DNA content, and lymph node metastases at the time of resection. However, whether the 10-year survival rates have also increased and are similarly predicted by these factors is not known. METHODS: The influence of preoperative imaging tests, alcohol consumption, cigarette smoking, K-ras mutations, anatomic location, details of surgical resection, pathologic findings, and tumor DNA content on survival was tested for 96 patients after a successful resection of a pancreatic carcinoma with 17 patients being followed for more than 5 years. RESULTS: The 5- and 10-year patient survival rates were 18% and 3%, respectively. Univariate and multivariable analyses showed that tumor DNA content, pathologic tumor size, and lymph node metastases were the strongest prognostic indicators for long-term patient survival, although the importance of tumor size may diminish 2 or more years after resection. Surprisingly, the 11 patients with diploid carcinomas > or = 4 cm had an estimated 10-year survival rate of 36%. CONCLUSION: These results show that the 10-year survival rate for pancreatic carcinoma remains very low, although the subset of patients with biologically favorable tumors has a prolonged survival and possible cure after resection.

Adenocarcinoma↗
PubMed1998

Water permeation barrier in isolated cutaneous newborn rat epidermis.

Abnormal water barrier function occurs in irritated skin and certain cutaneous diseases. Methods have been compared for separating the epidermis (site of the barrier) from the whole skin without disturbing the barrier function. The epidermis was separated from newborn rat skin by (1) exposure to 10% trypsin at 4 degrees C for 16 h, (2) exposure to 0.2% dispase at 4 degrees C for 16 h, (3) heating for 50 s at 55 degrees C, (4) or heating for 40 s at 50 degrees C after the whole skin was kept in medium at the air-liquid interface for 1 day at 35 degrees C. Water permeation of the isolated epidermis was then measured immediately or after 3, 5, 8, and 10 days of maintenance at the air-liquid interface. The water permeation barrier constant (kp) was 1.9+/-0.9 cm/h in intact rat skin. At 0 day of maintenance, the kp of the epidermis was 2.1+/-0.9 after treatment with trypsin, 3.8+/-1.2 after dispase, and 4.3+/-1.4 after immediate heating, or 2.2+/-0.7 cm/h after culture and heating. The dispase and heating methods disrupted the barrier to a greater extent than did the trypsin and culture-heating methods. The latter two methods allowed the kp to be maintained at low levels for 8 days (kp for trypsin 2.8+/-0.9 and 2.5+/-0.8 for culture-heating). Epidermis isolated by the trypsin or culture-heating techniques and maintained at the air-liquid interface can be used to study the mechanism by which barrier function is disrupted by chemicals.

Animals↗
PubMed1998

Induction and maintenance of increased VEGF protein by chronic motor nerve stimulation in skeletal muscle.

Vascular endothelial growth factor (VEGF) causes endothelial cell proliferation in vitro and angiogenesis in vivo. Glycolytic skeletal muscles have a lower capillary density than oxidative muscles but can increase their capillary density and convert to a more oxidative phenotype when subject to chronic motor nerve stimulation (CMNS). We used Western analysis and immunohistochemical techniques to examine VEGF protein in a rabbit CMNS model of glycolytic skeletal muscle and in muscles with innate glycolytic versus oxidative phenotypes. VEGF protein per gram of total protein was increased in stimulated vs. control muscles 2.9 +/- 1.0, 3.6 +/- 1.3, 3.1 +/- 0.5, 4.4 +/- 1.6, and 2.7 +/- 0.3 times after 3 (n = 4), 5 (n = 2), 10 (n = 3), 21 (n = 3), and 56 (n = 2) days, respectively. VEGF protein was increased 3.1 +/- 0.5 times (P < 0.005) before (3, 5, and 10 days) and remained elevated 3.7 +/- 1.0 times (P < 0.05) after (21 and 56 days) the transition to an oxidative phenotype. By immunohistochemistry, VEGF protein was found primarily in the matrix between stimulated muscle fibers but not in the myocytes. In addition, VEGF protein was consistently lower in innate glycolytic compared with oxidative muscles. These findings suggest that VEGF plays a role in the alteration and maintenance of vascular density in mammalian skeletal muscles.

Animals↗
PubMed1998

Metastatic germ cell tumors: modeling for response to chemotherapy.

PURPOSE: This study sought to determine factors that predict response to chemotherapy for patients with advanced germ cell tumors (GCTs), to evaluate different methods by which serum tumor markers can be used to predict response independent of assay method, and to develop criteria to guide allocation to clinical trials. METHODS: Pretreatment data from 796 patients treated with platinum-based chemotherapy on Memorial Hospital protocols from 1975 to 1990 were analyzed. Multivariate analyses were performed on a developmental data set (n = 597) to assess for independently significant predictors of response. Predictive models developed using these methods were confirmed on the validation set (n = 199). RESULTS: Independently significant factors for response included a mediastinal primary tumor (.015), pure seminomatous histology (.002), metastases to nonpulmonary visceral sites (bone, liver, and brain; .0001), and the pretreatment values of lactate dehydrogenase (LDH; .0001) and human chorionic gonadotropin (HCG; .0001). The likelihood of complete response (CR) was increased by seminomatous histology and decreased by the other factors. Serum levels of HCG and LDH could predict outcome independent of assay methodology. A model to predict good-, intermediate-, and poor-risk categories with CR rates of 92%, 76%, and 39%, respectively, was developed. CONCLUSION: The independent prognostic factors of serum tumor markers LDH and HCG, the sites of metastases, and the primary origin of GCTs can predict outcome in patients with advanced GCT. These factors should be considered in the allocation of patients with advanced disease to clinical trials and have been included in the new tumor-node-metastasis (TNM) staging systems developed for the American Joint Committee on Cancer (AJCC) and the Union Internationale Contre le Cancer (UICC).

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

BOD (Bcl-2-related ovarian death gene) is an ovarian BH3 domain-containing proapoptotic Bcl-2 protein capable of dimerization with diverse antiapoptotic Bcl-2 members.

Using the yeast two-hybrid protein-protein interaction system to search for genes capable of forming dimers with the antiapoptotic protein Mcl-1, we have isolated BOD (Bcl-2-related ovarian death agonist) from an ovarian fusion cDNA library. The three variants of BOD (long, medium, and short) have an open reading frame of 196, 110, and 93 amino acids, respectively; all of them contain a consensus Bcl-2 homology 3 (BH3) domain but lack other BH domains found in channel-forming Bcl-2 family proteins. In the yeast cell assay, BOD interacts with diverse antiapoptotic Bcl-2 proteins [Mcl-1, Bcl-2, Bcl-xL, Bcl-w, Bfl-1, and Epstein-Barr virus (EBV) BHRF-1] but not with different proapoptotic Bcl-2 proteins (BAD, Bak, Bok, and Bax). After overexpression in mammalian Chinese hamster ovary (CHO) cells, BOD induces apoptosis that can be prevented by the baculoviral caspase inhibitor P35. The cell-killing activity of BOD is also antagonized in cells cotransfected with the antiapoptotic Bcl-w protein, which showed high affinity for BOD in the two-hybrid assay. Furthermore, mutagenesis studies showed that BOD mutants with alterations in the BH3 domain lose cell-killing ability, suggesting that the BH3 domain is important for the mediation of cell killing by BOD. BOD mRNA is ubiquitously expressed in ovary and multiple other tissues. The BOD gene is also conserved in diverse mammalian species. Identification of BOD expands the group of proapoptotic Bcl-2 proteins that only contains the BH3 domain and allows future elucidation of the intracellular mechanism for apoptosis regulation in ovary and other tissues.

Alternative Splicing↗
PubMed1998

[Adjuvant chemotherapy following radical surgery for non-small cell lung cancer: a randomized study].

OBJECTIVE: To evaluate the efficacy of adjuvant chemotherapy after radical surgery for non-small cell lung cancer (NSCLC). METHODS: Seventy patients with NSCLC(stage I-III) undergone radical surgery were randomized into two groups: 35 patients received adjuvant chemotherapy with cyclophosphamide (CTX) 300 mg/m2, vincristine(VCR) 1.4 mg/m2, adriamycin(ADM) 50 mg/m2, d1; cisplatin (PDD) 20 mg/m2, d1-5, for 4 cycles, and followed by oral ftorafur (FT-207) 600-900 mg/d for 1 year (adjuvant chemotherapy group). The other 35 patients received surgical treatment only (surgery group). RESULTS: The overall 5-year survival rate was 48.6% in the adjuvant chemotherapy group, and 31.4% in the surgery group, respectively. The difference between the two groups was not statistically significant (P > 0.05). The 5-year survival rate of patients in atage III was 44.0% and 20.8% (5/24) received surgery with and without adjuvant chemotherapy, respectively. The difference between the two groups was statistically significant (P < 0.025). The 5-year survival rate of patients in stage I-II in the two group was 60.0% and 54.5%, respectively (P > 0.75). CONCLUSION: Postoperative adjuvant chemotherapy in NSCLC improves survival but only in patients in stage III, it results in significantly higher 5-year susvival rate than surgery alone.

Adult↗
PubMed1998

[Chemoprevention of esophageal cancer].

OBJECTIVE: Our goal was to test and pursue the achievement achieved in Heshun township of Linxian county, Henan province. Since 1992, we have been conducting block therapy for precancerous lesions of the esophagus in 9 townships of Ci county, Hebei province, a high risk area of esophageal cancer. METHODS: By means of a cytological survey, 3,990 and 5,346 cases of severe and mild dysplasia of esophageal epithelium were selected. These cases are divided randomly into the treated group and the control group. In the treated group, the Chinese herbal medicine Zeng Sheng Ping were given to the patients with severe dysplasia, and tablets of riboflavin Calcium were given to the patients with mild dysplasia. Placebo were given to the control group. After administration of drugs for 3 years, the esophageal cytological reexamination was repeated in July 1996. RESULTS: In the severe dysplasia treated group, RR = 0.50, 95% CI = 0.33-0.75, inhibitory rate of canceration 49.9%; using the method of cytological five grade-six kinds as the mark of standard to calculate the general grade effects, and using the control group as the standard group, the treated group Ridit = 0.58, 95% CI = 0.56-0.60; in the mild dysplasia treated group, RR = 0.80, 95% CI = 0.52-1.22, inhibitory rate 20.4%; Ridit = 0.59, 95% CI = 0.57-0.61. CONCLUSIONS: These herbal blocking results indicated that the effects of the Chinese herbal medicine Zeng Sheng Ping on esophageal precancerous lesions were worthy of being highly considered.

Adult↗
PubMed1998

Inhibition of tumor growth by targeting tumor endothelium using a soluble vascular endothelial growth factor receptor.

Vascular endothelial growth factor (VEGF) is a leading candidate for an endogenous mediator of tumor angiogenesis. Recently, two endothelial cell surface receptors, flk-1 and flt-1, have been shown to mediate the angiogenic activities of VEGF. In this study, we have evaluated whether a soluble VEGF receptor could suppress tumor angiogenesis and thereby inhibit tumor growth. A soluble VEGF receptor was constructed by fusing the entire extracellular domain of murine flk-1 to a six-histidine tag at the COOH terminus (ExFlk.6His). In vitro, recombinant ExFlk.6His protein bound VEGF with high affinity (Kd, 16 nM) and blocked receptor activation in a dose-dependent manner and inhibited VEGF-induced endothelial cell proliferation and migration. ExFlk.6His bound to endothelial cells only in the presence of VEGF, and cell surface cross-linking yielded a high molecular weight complex consistent with the VEGF-mediated formation of a heterodimer between ExFlk.6His and the endogenous VEGF receptor. In vivo, ExFlk.6His potently inhibited corneal neovascularization induced by conditioned media from a rat mammary carcinoma cell line (R3230AC). Moreover, when ExFlk.6His protein was administered into a cutaneous tumor window chamber concomitantly with R3230AC carcinoma transplants, tumor growth was inhibited by 75% (P < 0.005) and vascular density was reduced by 50% (P < 0.002) compared with control-treated tumors. These results demonstrate the potential of ExFlk.6His to inhibit VEGF action by a potent "dominant-negative" mechanism and suggest that targeting VEGF action using a soluble receptor may be an effective antiangiogenic therapy for cancer and other "angiogenic" diseases.

Animals↗
PubMed1998

Concentrations of carotenoids, tocopherols, and retinol in paired plasma and cervical tissue of patients with cervical cancer, precancer, and noncancerous diseases.

Paired blood (collected after an overnight fast) and cervical tissue (cancerous, precancerous, and noncancerous) samples were obtained from 87 patients (age, 21-86 years) who had a hysterectomy or biopsy due to cervical cancer, precancer (cervical intraepithelial neoplasia I, II, and III), or noncancerous diseases. The samples were analyzed using high-performance liquid chromatography for 10 micronutrients (lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene, beta-carotene, cis-beta-carotene, alpha-tocopherol, gamma-tocopherol, and retinol). The results indicated that: (a) among the three patient groups, the mean plasma concentrations of all micronutrients except gamma-tocopherol were lowest in the cancer patients; however, the mean tissue concentrations of the two tocopherols and certain carotenoids were highest in the cancerous tissue; and (b) among the 10 micronutrients, only the concentrations of beta-carotene and cis-beta-carotene were lower in both the plasma and tissue of cancer and precancer patients than in those of noncancer controls. These results suggest that: (a) not all of the micronutrient concentrations in plasma reflect the micronutrient concentrations in cervical tissue; thus, in some cases, it may be necessary to measure the tissue micronutrient concentrations to define the role of the micronutrients in cervical carcinogenesis; and (b) maintaining an adequate plasma and tissue concentration of beta-carotene may be necessary for the prevention of cervical cancer and precancer.

Adult↗
PubMed1998

Status of deleted in colorectal cancer gene expression correlates with neuroblastoma metastasis.

Neuroblastoma is an embryonal tumor of neural crest origin noted for its heterogeneity at the clinical, histologic, and molecular levels. The deleted in colorectal cancer (DCC) protein is an adhesion family molecule of unequivocal importance in neural development that has also been implicated in several malignancies, including neuroblastoma, through its apparent loss of function. Immunohistochemical assessment of the DCC protein was performed on a group of 49 neuroblastoma specimens and examined in relation to important clinical, histologic, and molecular parameters. DCC expression was significantly associated with neuroblastoma dissemination as primary tumors from Stage 1 to 3 patients (15/20, 75%) more frequently exhibited the DCC protein than those from Stage 4 patients (5/13, 38%; p = 0.0415). Primary tumors were more frequently DCC-positive (20/33, 61%) as compared with metastatic deposits (3/16, 19%; p = 0.0063), and a single case of a paired primary and metastatic deposit demonstrated the apparent loss of DCC gene expression with tumor progression. The remaining five paired specimens were DCC-negative in both the primary tumor and metastatic deposit. No significant association was appreciated between DCC expression and patient age, the Shimada histologic classification, or N-Myc amplification. These results provide evidence that DCC expression may be lost in the course of metastatic spread in a subset of neuroblastomas. Moreover, DCC function is implicated in neuroblastoma dissemination in a manner independent of N-Myc.

Cell Adhesion Molecules↗
PubMed1997

Inhibition of tumor angiogenesis using a soluble receptor establishes a role for Tie2 in pathologic vascular growth.

Tie2 is a novel receptor tyrosine kinase that is expressed almost exclusively by vascular endothelium. Disruption of Tie2 function in transgenic mice resulted in embryonic lethality secondary to characteristic vascular defects; similar defects occurred after disruption of the Tie2 ligand. These findings indicate that the Tie2/Tie2 ligand pathway plays important roles during development of the embryonic vasculature. To determine whether the Tie2 pathway was involved in pathologic angiogenesis in adult tissues, a soluble form of the extracellular domain of murine Tie2 (ExTek.6His) was developed and used as a Tie2 inhibitor. After a single application of the ExTek.6His protein into a rat cutaneous window chamber, growth of a mammary tumor inside the chamber was reduced by > 75% (P < 0.005), and tumor vascular length density was reduced by 40% when compared with control-treated tumors (P < 0.01). In the rat cornea, ExTek.6His blocked angiogenesis stimulated by tumor cell conditioned media. ExTek.6His protein did not affect the viability of cultured tumor cells, indicating that the antitumor effect of ExTek.6His was due to the inhibition of tumor angiogenesis. These data demonstrate a role for the Tie2 pathway in pathologic angiogenesis, suggesting that targeting this pathway may yield effective antiangiogenic agents for treatment of cancer and other angiogenic diseases.

Animals↗
PubMed1997

Chromosome 19 single-locus and multilocus haplotype associations with multiple sclerosis. Evidence of a new susceptibility locus in Caucasian and Chinese patients.

CONTEXT: Susceptibility to multiple sclerosis (MS) involves a genetically complex autoimmune component. However, except for genes in the HLA system, specific susceptibility loci are unknown or unconfirmed. OBJECTIVE: To investigate several loci spanning 3 candidate regions for a role in multiple sclerosis (MS) susceptibility in 2 ethnic groups using both single-locus and haplotype analyses. The 3 regions include HLA on chromosome 6p21.3, APOE on chromosome 19ql 3.2, and MBP(myelin basic protein) on chromosome 18q23. DESIGN: Case-control association testing. SUBJECTS: A total of 120 Caucasian patients with MS and 107 unrelated control individuals from California, and 32 patients and 32 unrelated control individuals from Beijing, China. All patients with MS were diagnosed as having clinically definite disease according to published criteria. MAIN OUTCOME MEASURES: Chi2 Testing of loci and individual alleles and haplotypes. Haplotype frequencies were estimated with standard maximum likelihood methods. RESULTS: The HLA effect is due to the class II DR2 haplotype, DRB1*1501-DQA1*0102-DRB1*0602; contributions to MS susceptibility from additional DRB1-DQB1 alleles or other HLA region loci were not observed. Variation within the MBP locus on chromosome 18q23 showed no effect in MS. The distribution of haplotypes from 5 loci within the chromosome 19q13.2 region, including D19S178, D19S574, APOE, APOC2, and D19S219, differed between patient and control samples. D19S574 showed a significant effect (P=.015) in Caucasian patients with MS due to the increased frequency of a single allele (P=.002). The APOE variation, prominent in other neurological diseases, showed no influence on MS susceptibility, despite its location within the chromosome 19q13.2 region. Interaction effects between DR2 and chromosome 19q13.2 or MBP in MS susceptibility were not apparent. CONCLUSIONS: The significant chromosome 19q13.2 single-locus and multilocus haplotype associations with MS in Caucasian and Chinese patient samples indicate an effect from a nearby disease susceptibility locus. These initial observations are an encouraging step toward the description of non-HLA genetic susceptibility to MS.

Alleles↗
PubMed1997

The unique hetero-oligomeric nature of the subunits in the catalytic cooperativity of the yeast Cct chaperonin complex.

The structural and functional organization of the Cct complex was addressed by genetic analyses of subunit interactions and catalytic cooperativity among five of the eight different essential subunits, Cct1p-Cct8p, in the yeast Saccharomyces cerevisiae. The cct1-1, cct2-3, and cct3-1 alleles, containing mutations at the conserved putative ATP-binding motif, GDGTT, are cold-sensitive, whereas single and multiple replacements of the corresponding motif in Cct6p are well tolerated by the cell. We demonstrated herein that cct6-3 (L19S), but not the parolog cct1-5 (R26I), specifically suppresses the cct1-1, cct2-3, and cct3-1 alleles, and that this suppression can be modulated by mutations in a putative phosphorylation motif, RXS, and the putative ATP-binding pocket of Cct6p. Our results suggest that the Cct ring is comprised of a single hetero-oligomer containing eight subunits of differential functional hierarchy, in which catalytic cooperativity of ATP-binding/hydrolysis takes place in a sequential manner different from the concerted cooperativity proposed for GroEL.

Amino Acid Sequence↗
PubMed1997

Bispecific humanized anti-IL-2 receptor alpha beta antibodies inhibitory for both IL-2- and IL-15-mediated proliferation.

Humanized anti-Tac (HAT) and Mik beta1 (HuMik beta 1) Abs directed at IL-2R alpha and IL-2R beta, respectively, inhibit IL-2 binding and biological activity and together act synergistically in vitro. The Abs have been used successfully in primate models of allograft rejection, graft-vs-host disease, and autoimmunity. We produced bifunctional humanized anti-IL-2R alpha beta Abs (BF-IgG) to combine the specificity of the two Abs into one entity by fusing HAT-producing NSO cells and HuMik beta 1-producing Sp2/0 cells. BF-IgG was purified using protein G-Sepharose affinity chromatography, followed by IL-2R alpha and IL-2R beta affinity chromatography and hydrophobic interaction chromatography. BF-IgG exhibited both anti-IL-2R alpha and anti-IL-2R beta specificities in binding assays. While the Ab binds the IL-2R with intermediate affinity (Kd = 2.82 nM), it does not inhibit IL-15 binding to its high affinity IL-15R. In Kit225/K6 (IL-2R alpha beta gamma+) cells, BF-IgG was 10-fold more potent than a HAT/HuMik beta 1 equimolar mixture in blocking IL-2-induced proliferation and, unexpectedly, was at least 65-fold more active than the mixture in blocking IL-15-induced proliferation. This dual inhibitory activity may be due to cross-linking of the IL-2R alpha and IL-2R beta, thus blocking IL-2 binding and possibly impeding the association of IL-2R beta with IL-15R. BF-IgG has potent immunosuppressant activities against both IL-2- and IL-15-mediated responses, and this antagonist could be more efficacious than HAT and/or HuMik beta 1 for the treatment of autoimmunity and the prevention of allograft rejection.

Antibodies, Bispecific↗
PubMed1997

In vivo modification of the C-terminal lysine of human lens alphaB-crystallin.

Both the structural and chaperone-like properties of lens alpha-crystallins have been implicated in maintaining lens transparency. Modifications of lens alpha-crystallins may lead to formation of cataract by affecting the close-packing of the crystallins or by reducing the chaperone-like activity of the alpha-crystallins. A previously unreported modified alphaB-crystallin, whose molecular weight is 72 u greater than unmodified alphaB-crystallin, has been isolated from human lenses by size exclusion chromatography, reversed phase HPLC and ion exchange HPLC. Approximately one nanomole of this modified alphaB-crystallin was obtained from each of five human eye lenses. Molecular weight determinations of peptides produced by digestion with trypsin or endoproteinase Asp-N showed that the modification is in the C-terminal region of alphaB-crystallin. The fragmentation pattern of peptides from the C-terminal region, analysed by tandem mass spectrometry, located the modification of the epsilon-amino group of the C-terminal lysine. The elemental composition of this modification, determined from its exact mass, is C3H4O2. Because this modification decreases the net charge of alphaB-crystallin by one unit, and because the C-terminus has been implicated in the chaperone activity attributed to alphaB-crystallin, this modification at Lys 175 may have a significant role in cataractogenesis.

Adult↗
PubMed1997

Neutralizing IGF-1 monoclonal antibody with cross-species reactivity.

We report the generation of a murine IGF-1 monoclonal antibody designated 35I17, which exhibits unique cross-species reactivity. The antibody recognizes recombinant human and rat IGF-1 in ELISA, Western blots, and in an 125I-recombinant human IGF-1 Scintillation Proximity Assay. In addition, 35I17 blocks cell proliferation induced by recombinant human and rat IGF-1, and inhibits cell proliferation induced by sera from human, rat, calf, dog, goat, or mouse. The antibody inhibits rat IGF-1 binding to IGF-1 receptors, and prevents IGF-1-stimulated receptor and IRS-1 phosphorylation in LISN C4 cells, an IGF-1 receptor-transfected cell line. The cross-species and neutralizing properties of 35I17 may be useful in in vitro and in vivo animal studies for elucidating the role of IGF-1 in cancer, rheumatoid arthritis, and other diseases.

3T3 Cells↗
PubMed1997

Analysis of mutationally altered forms of the Cct6 subunit of the chaperonin from Saccharomyces cerevisiae.

The Cct double-ring chaperonin complex of Saccharomyces cerevisiae is comprised of eight essential subunits, Cct1p-Cct8p, and assists the folding of substrates such as actins and tubulins. Single and multiple amino acid replacements of Cct6p were constructed by oligonucleotide-directed mutagenesis, including changes of charged to alanine residues and uncharged to charged residues. The replacements were targeted, in part, to residues corresponding to functionally critical regions identified in the published crystal structure of the Escherichia coli chaperonin, GroEL. Here, we report the critical hydrophobic residues and clusters of hydrophilic residues in regions corresponding to those from the apical domain of GroEL implicated in peptide binding and peptide release, and certain residues in the putative equatorial domain implicated in subunit-to-subunit interaction. In contrast to their homologous counterparts in Cct2p and Cct1p, the highly conserved putative ATP binding motifs of Cct6p were relatively amenable to mutations. Our data suggest that the entire Cct6p molecule might be essential for assembly of Cct complex and might participate in binding substrates. However, there appeared to exist a functional hierarchy in ATP binding/hydrolysis among Cct subunits, as suggested by the high tolerance of Cct6p to mutations within the putative ATP binding pocket.

Amino Acid Sequence↗