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FitzHugh ZT, Schiller MR. Systematic Assessment of Protein C-Termini Mutated in Human Disorders. Biomolecules 2023; 13:biom13020355. [PMID: 36830724 PMCID: PMC9953674 DOI: 10.3390/biom13020355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/23/2023] [Accepted: 02/02/2023] [Indexed: 02/16/2023] Open
Abstract
All proteins have a carboxyl terminus, and we previously summarized eight mutations in binding and trafficking sequence determinants in the C-terminus that, when disrupted, cause human diseases. These sequence elements for binding and trafficking sites, as well as post-translational modifications (PTMs), are called minimotifs or short linear motifs. We wanted to determine how frequently mutations in minimotifs in the C-terminus cause disease. We searched specifically for PTMs because mutation of a modified amino acid almost always changes the chemistry of the side chain and can be interpreted as loss-of-function. We analyzed data from ClinVar for disease variants, Minimotif Miner and the C-terminome for PTMs, and RefSeq for protein sequences, yielding 20 such potential disease-causing variants. After additional screening, they include six with a previously reported PTM disruption mechanism and nine with new hypotheses for mutated minimotifs in C-termini that may cause disease. These mutations were generally for different genes, with four different PTM types and several different diseases. Our study helps to identify new molecular mechanisms for nine separate variants that cause disease, and this type of analysis could be extended as databases grow and to binding and trafficking motifs. We conclude that mutated motifs in C-termini are an infrequent cause of disease.
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Affiliation(s)
- Zachary T. FitzHugh
- Nevada Institute of Personalized Medicine, University of Nevada Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154, USA
- School of Life Sciences, University of Nevada, 4505 S. Maryland Parkway, Las Vegas, NV 89154, USA
| | - Martin R. Schiller
- Nevada Institute of Personalized Medicine, University of Nevada Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154, USA
- School of Life Sciences, University of Nevada, 4505 S. Maryland Parkway, Las Vegas, NV 89154, USA
- Heligenics Inc., 833 Las Vegas Blvd. North, Suite B, Las Vegas, NV 89101, USA
- Correspondence: ; Tel.: +1-702-895-5546; Fax: +1-702-895-5728
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2
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Affiliation(s)
- David C. Klonoff
- Diabetes Research Institute,
Mills-Peninsula Medical Center, San Mateo, CA, USA
- David C. Klonoff, MD, FACP, FRCP (Edin),
Fellow AIMBE, Diabetes Research Institute, Mills-Peninsula Medical Center, 100 S
San Mateo Dr, Rm 5147, San Mateo, CA 94401, USA.
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Shepherd JRA, Dominelli PB, Roy TK, Secomb TW, Hoyer JD, Oliveira JL, Joyner MJ. Modelling the relationships between haemoglobin oxygen affinity and the oxygen cascade in humans. J Physiol 2019; 597:4193-4202. [PMID: 31290158 DOI: 10.1113/jp277591] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 07/08/2019] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity impact physiology is unknown. Using human haemoglobin variants, we demonstrate that the affinity of haemoglobin for oxygen is highly correlated with haemoglobin concentration. Using the Fick equation, we model how altered haemoglobin affinity and the associated haemoglobin concentration influences oxygen consumption at rest and during exercise via alterations in cardiac output and mixed-venous P O 2 . The combination of low oxygen affinity haemoglobin and reduced haemoglobin concentration seen in vivo may be unable to support oxygen uptake during moderate or heavy exercise. ABSTRACT The physiological implications, with regard to exercise, of altered haemoglobin affinity for oxygen are not fully understood. Data from the Mayo Clinic Laboratories database of rare human haemoglobin variants reveal a strong inverse correlation (r = -0.82) between blood haemoglobin concentration and P50 , an index of oxygen affinity [Hb = -0.3135(P50 ) + 23.636]. In the present study, observed P50 values for high, normal and low oxygen-affinity haemoglobin variants (13, 26 and 39 mmHg) and corresponding haemoglobin concentrations (19.5, 15.5 and 11.4 g dL-1 respectively) are used to model oxygen consumption as a fraction of delivery at rest ( V ̇ O 2 = 0.25 L min-1 , cardiac output = 5.70 L min-1 ) and during exercise ( V ̇ O 2 = 2.75 L min-1 , cardiac output = 18.9 l min-1 ). With high-affinity haemoglobin, the model shows that normal levels of oxygen consumption can be achieved at rest and during exercise at the assumed cardiac output levels, with reduced oxygen extraction both at rest (16.8% high affinity vs. 21.7% normal) and during exercise (55.8% high affinity vs. 72.2% normal). With low-affinity haemoglobin, which predicts low haemoglobin concentration, oxygen consumption at rest can be sustained with the assumed cardiac output, with increased oxygen extraction (31.1% low affinity vs. 21.7% normal). However, exercise at 2.75 l min-1 cannot be achieved with the assumed cardiac output, even with 100% oxygen extraction. In conclusion, the model indicates chronic alterations in P50 associate directly with Hb concentration, highlighting that human Hb variants can serve as 'experiments of nature' to address fundamental hypotheses on oxygen transport and exercise.
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Affiliation(s)
- John R A Shepherd
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Paolo B Dominelli
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Kinesiology, University of Waterloo, Waterloo, ON, USA
| | - Tuhin K Roy
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Timothy W Secomb
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - James D Hoyer
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Jennifer L Oliveira
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Michael J Joyner
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
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Substitutions in woolly mammoth hemoglobin confer biochemical properties adaptive for cold tolerance. Nat Genet 2010; 42:536-40. [DOI: 10.1038/ng.574] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 03/31/2010] [Indexed: 11/08/2022]
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Tefferi A, Pardanani A. Evaluation of "increased" hemoglobin in the JAK2 mutations era: a diagnostic algorithm based on genetic tests. Mayo Clin Proc 2007; 82:599-604. [PMID: 17493421 DOI: 10.4065/82.5.599] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Recent discoveries in the molecular pathogenesis of both polycythemia vera (PV) and congenital polycythemia (CP) underline the prospect of a genetic diagnosis in these disorders. At the forefront are the mutually exclusive exon 14 (JAK2V617F) and exon 12 JAK2 mutations that are almost always present in PV but not in polycythemias of other causes. Similarly, the molecular basis of CP is being unraveled, and several cases are now associated with germline mutations involving the von Hippel-Lindau (VHL) or erythropoietin receptor (EPOR) genes. Therefore, current diagnostic work-up for acquired polycythemia should start with peripheral blood JAK2 mutation screening, whereas VHL and/or EPOR mutations should be considered when CP is suspected. In all instances, serum erythropoietin measurement provides complementary information; the serum erythropoietin level is expected to be decreased in PV regardless of JAK2 mutation status, increased in VHL mutation-associated CP, and decreased or normal in the presence of an EPOR mutation.
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Affiliation(s)
- Ayalew Tefferi
- Division of Hematology, College of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
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Shannon KM, Clemons GK, Torkildson JC, Buchanan GR, Mentzer WC. Spontaneous resolution of primary erythrocytosis in two girls. Pediatr Hematol Oncol 1989; 6:373-82. [PMID: 2641707 DOI: 10.3109/08880018909034310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We report two girls with primary erythrocytosis in whom extensive diagnostic studies revealed no underlying cause. Normal growth of colonies derived from erythroid burst forming units (BFU-E) was observed, and serum erythropoietin concentrations were within or below the normal range. The absence of a rise in serum erythropoietin levels after isovolemic phlebotomy implicated the erythroid marrow as the site of the pathophysiologic abnormality in both patients. Spontaneous resolution of erythrocytosis occurred during the second decade of life. Our experience suggests that primary erythrocytosis may be self-limited in some children. In these cases, the proliferative abnormality may be sufficiently subtle as to not be detected by standard in vitro culture systems, which support the growth of colonies derived from erythroid progenitors.
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Affiliation(s)
- K M Shannon
- Department of Pediatrics, University of California School of Medicine, San Francisco
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McDonald MJ, Turci SM, Bleichman M, Stinson RA. Functional and subunit assembly properties of hemoglobin Alberta (alpha 2 beta 2(101) Glu----Gly). J Mol Biol 1985; 183:105-12. [PMID: 4009719 DOI: 10.1016/0022-2836(85)90284-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Hemoglobin Alberta has an amino acid substitution at position 101 (Glu----Gly), a residue involved in the alpha 1 beta 2 contact region of both the deoxy and oxy conformers of normal adult hemoglobin. Oxygen equilibrium measurements of stripped hemoglobin Alberta at 20 degrees C in the absence of phosphate revealed a high affinity (P50 = 0.75 mm Hg at pH 7), co-operative hemoglobin variant (n = 2.3 at pH 7) with a normal Bohr effect (- delta log P50/delta pH(7-8) = 0.65). The addition of inositol hexaphosphate resulted in a decrease in oxygen affinity (P50 = 8.2 mm Hg at pH 7), a slight increase in the value of n and an enhanced Bohr effect. Rapid mixing experiments reflected the equilibrium results. A rapid rate of carbon monoxide binding (l' = 7.0 X 10(5) M-1 S-1) and a slow rate of overall oxygen dissociation (k = 15 s-1) was seen at pH7 and 20 degrees C in the absence of phosphate. Under these experimental conditions the tetramer stability of liganded and unliganded hemoglobin Alberta was investigated by spectrophotometric kinetic techniques. The 4K4 value (the liganded tetramer-dimer equilibrium dissociation constant) for hemoglobin Alberta was found to be 0.83 X 10(-6) M compared to a 4K4 value for hemoglobin A of 2.3 X 10(-6) M, indicating that the Alberta tetramer was less dissociated into dimers than the tetramer of hemoglobin A. The values of 0K4 (the unliganded tetramer-dimer equilibrium dissociation constant) for hemoglobin Alberta and hemoglobin A were also measured and found to be 2.5 X 10(-8) M and 1.5 X 10(-10) M, respectively, demonstrating a greatly destabilized deoxyhemoglobin tetramer for hemoglobin Alberta compared to deoxyhemoglobin A. The functional and subunit dissociation properties of hemoglobin Alberta appear to be directly related to the dual role of the beta 101 residue in stabilizing the tetrameric form of the liganded structure, while concurrently destabilizing the unliganded tetramer molecule.
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Stinson RA. Asymmetric hybrids formed with hemoglobin British Columbia (alpha 2 beta 2101Glu----Lys). Hemoglobin 1984; 8:483-96. [PMID: 6500987 DOI: 10.3109/03630268408991733] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Whole blood and purified hemoglobins from a patient heterozygous for Hb British Columbia were studied with various types of electrophoresis. Isoelectric focusing of whole blood in cylindrical polyacrylamide gels showed 3 major hemoglobin species at equilibrium: Hb A, Hb British Columbia, and an unidentified Hb with an isoelectric point of 7.15. In addition, a transient asymmetric hybrid band was observed between Hb A and Hb British Columbia; it had disappeared at equilibrium. Hb A2 was never present. Isoelectric focusing of purified Hbs A2 and British Columbia in various proportions, and gel permeation chromatography of them in equal amounts, indicated that the pI 7.15 component was a very stable hybrid. This hybrid was recovered from thin-layer isoelectric focusing in agarose. Electrophoresis on agar at pH 6.0 showed 3 hemoglobins: A2, British Columbia, and one of intermediate migration. On cellulose acetate at pH 9.2, only the 2 parent Hb components, A2 and British Columbia were seen. Thus, the single Hb recovered from agarose is probably the asymmetric hybrid alpha 2 delta beta British Columbia.
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Wranne B, Berlin G, Jorfeldt L, Lund N. Tissue oxygenation and muscular substrate turnover in two subjects with high hemoglobin oxygen affinity. J Clin Invest 1983; 72:1376-84. [PMID: 6630512 PMCID: PMC370422 DOI: 10.1172/jci111094] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Oxygen transport to and substrate turnover in leg muscle were studied at rest and during light and heavy upright bicycle exercise in two brothers with a hereditary hemoglobinopathy associated with high oxygen affinity (P50 = 13 mmHg). Femoral venous oxygen tension was below normal and femoral venous oxygen saturation above normal at rest and during exercise. Thus, the arterial-femoral venous oxygen saturation difference was decreased. Despite a compensatory increase in hemoglobin concentration, the arterial-femoral venous oxygen content difference tended to be below normal at heavy exercise. Approximately 25% of the oxygen was delivered via the abnormal hemoglobin at relative heavy exercise. Arterial lactate levels, lactate release, and muscle lactate concentration were not increased at any level of exercise. Glucose, alanine, pyruvate, and glycerol turnover were essentially normal, but the glycogen and creatine phosphate stores were abnormally depleted at the termination of heavy exercise. The exercise electrocardiogram (ECG) was normal, indicating that myocardial oxygenation was adequate. Muscle-surface oxygen pressure fields were normal at rest (not investigated during exercise). It is concluded that the high oxygen affinity of the hemoglobin in our two subjects did not lead to heart or skeletal muscle hypoxia during heavy exercise, as judged from the ECG and from the leg lactate turnover. Despite the lack of evidence for muscle hypoxia, the subjects experienced leg muscle fatigue and the creatine phosphate and glycogen stores were depleted more than normally.
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Como PF, Kennett D, Wilkinson T, Kronenberg H. A new hemoglobin with high oxygen affinity--hemoglobin bunbury: alpha 2 beta 2 [94 (FG1) Asp replaced by Asn]. Hemoglobin 1983; 7:413-21. [PMID: 6629823 DOI: 10.3109/03630268309038410] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Hemoglobin Bunbury was detected in an Italian woman from Bunbury, Western Australia, following detection of an abnormal hemoglobin by electrophoresis. The variant form accounted for 38% of the total hemoglobin and migrated on cellulose acetate electrophoresis between HbS and HbA. Structural analysis demonstrated a new substitution in the beta chain, beta 94 Asp replaced by Asn. Hemoglobin Bunbury is stable to both heat and isopropanol denaturation. This variant shows an increase in oxygen affinity and a reduced Bohr effect. Heterozygosity for Hb Bunbury produces no clinical symptoms or compensatory erythrocytosis.
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Quarum M, Shih T, Jones RT. Oxygen equilibrium studies of Hb Willamette alpha 2 beta (2)51(D2)Pro leads to Arg. Hemoglobin 1983; 7:57-69. [PMID: 6841127 DOI: 10.3109/03630268309038401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The homotropic and heterotropic effects of isolated Hb Willamette were studied using an automatic recording oxygen equilibrium analyzer. The results indicate that Hb Willamette displays normal intrinsic oxygen binding in the stripped condition. An apparent decrease of the Bohr effect is explained by the decrease of allosteric effects in this abnormal hemoglobin. Furthermore, the lack of clinical manifestations in the original patient is consistent with the red cell oxygen equilibrium studies.
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Wajcman H, Aguilar i Bascompte JL, Labie D, Poyart C, Bohn B. Structural and functional studies of hemoglobin Barcelona (alpha 2 beta 2 94 Asp (FG1) replaced by His). Consequences of altering an important intrachain salt bridge involved in the alkaline Bohr effect. J Mol Biol 1982; 156:185-202. [PMID: 7097767 DOI: 10.1016/0022-2836(82)90466-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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