Analysis of the nucleotide context of Arabidopsis thaliana mitochondrial mRNA editing sites

We have studied the effects of 1 mM solutions of L-amino acids on the X-ray- and heat-induced generation of hydrogen peroxide and hydroxyl radicals in phosphate buffer (5 mM, pH 7.4). Hydrogen peroxide was estimated by enhanced chemiluminescence in the luminol/p-iodophenol/peroxidase system; hydroxyl radicals were detected with a fluorescent probe coumarin-3-carboxylic acid. We demonstrate that amino acids can be grouped into three categories by their effect on X-ray-induced H₂O₂ production: those that reduce, increase, and have no influence on H₂O₂ yield. Similar amino acid effects were observed upon heating; however, the composition of respective amino acid groups was different. All amino acids lowered the X-ray-induced hydroxyl radical production, and the most effective were Cys > His > Phe = Met = Trp > > Tyr (in descending order). Hydroxyl radical generation induced by heating was inhibited by Met, His, and Phe; enhanced by Ser; and not affected by Tyr and Pro. Thus, amino acids have different effects on the production of reactive oxygen species by X-rays and heating, and some amino acids appear to be effective natural antioxidants.     

Effect of amino acids on X-ray-induced hydrogen peroxide and hydroxyl radical formation in water and 8-oxoguanine in DNA

Generation of hydrogen peroxide and hydroxyl radicals in L-amino acid solutions in phosphate buffer, pH 7.4, under X-ray irradiation was determined by enhanced chemiluminescence in the luminol-p-iodophenol-peroxidase system and using the fluorescent probe coumarin-3-carboxylic acid, respectively. Amino acids are divided into three groups according to their effect on the hydrogen peroxide formation under irradiation: those decreasing yield of H2O2, having no effect, and increasing its yield. All studied amino acids at 1 mM concentration decrease the yield of hydroxyl radicals in solution under X-ray irradiation. However, the highest effect is observed in the order: Cys > His > Phe = Met = Trp > Tyr. At Cys, Tyr, and His concentrations close to physiological, the yield of hydroxyl radicals decreases significantly. Immunoenzyme analysis using monoclonal antibodies to 8-oxoguanine (8-oxo-7,8-dihydroguanine) was applied to study the effect of amino acids with the most pronounced antioxidant properties (Cys, Met, Tyr, Trp, Phe, His, Lys, Arg, Pro) on 8-oxoguanine formation in vitro under X-ray irradiation. It is shown that amino acids decrease the content of 8-oxoguanine in DNA. These amino acids within DNA-binding proteins may protect intracellular DNA against oxidative damage caused by formation of reactive oxygen species in conditions of moderate oxidative stress.     

Lysozyme modification by the fenton reaction and gamma radiation

A comparative study was performed on lysozyme modification after exposure to Fenton reagent (Fe(II)/H2 O2) or hydroxyl radicals produced by y radiation. The conditions were adjusted to obtain, with both systems, a 50% loss of activity of the modified ensemble. Gamma radiation modified almost all types of amino acid residues in the enzyme, with little specificity. The modification order was Tyr > Met = Cys > Lys > Ile + Leu > Gly > Pro = Phe > Thr + Ala > Trp = Ser > Arg > Asp + Glu, with 42 mol of modified residues per initial mole of native enzyme. In contrast, when the enzyme was exposed to the Fenton reaction, only some types of amino acids were modified. Furthermore, a smaller number of residues (13.5) were damaged per initial mole of enzyme. The order of the modified residues was Tyr > Cys > Trp > Met His > Ile + Leu > Val > Arg. These results demonstrate that the modifications elicited by these two free radical sources follow different mechanisms. An intramolecular free radical chain reaction is proposed to play a dominant role in the oxidative modification of the protein promoted by gamma radiation.     

EPR characterization of free radical intermediates formed during ultrasound exposure of cell culture media

Free radicals and/or hydrogen peroxide produced by exposure of cells to ultrasound are potentially cytotoxic and mutagenic. The formation and type of free radical species can be substantially modulated by the chemical composition of the media in which the ultrasound exposures of cells are carried out. In the current study, we examined the free radical intermediates formed during ultrasound exposure of a typical cell culture medium (RPMI-1640); the dominant free radicals that were identified by spin trapping were derived from the hydrophobic amino acids Trp, Leu, and Phe, and were formed by hydrogen abstraction from these amino acids. Compared to exposures in phosphate-buffered saline, the yield of *OH radicals and H2O2 was significantly reduced in the cell culture medium, glucose (the main organic component in the medium), and the hydrophobic amino acids (Trp, Phe, Tyr, Leu, Val, Met) being chiefly responsible for this effect. In contrast, other nonhydrophobic amino acids did not contribute significantly to the *OH or H2O2 decrease. These findings are consistent with the accumulation of hydrophobic solutes at the liquid-gas interface of the collapsing cavitation bubbles resulting in increased efficiency of radical scavenging.     

Long-lived radicals of amino acids induced by X-ray-radiation are the source of hydrogen peroxide in aqueous medium

The formation of long-lived radicals in the solutions of casein and its hydrolysate with an equimolar mixture of amino acids was compared by measuring the X-ray-induced chemiluminescence. It was shown that free amino acids constituting the protein produce long-lived radicals. It was demonstrated that some amino acids (Leu, Ile, Val, Ser, Trp, Met, Pro, Arg, Gly, Phe) emit light of visible spectrum over a long period of time after the irradiation, which indicates the generation of long-lived radicals of these amino acids. The half-life times of these radicals are several hours. Dissolving irradiated dry amino acids capable of luminescing over a long time gives rise to the formation of hydrogen peroxide in aqueous medium.     

Long-lived radicals of amino acids induced by X-ray radiation are the source of hydrogen peroxide in aqueous medium

Formation of long-lived radicals in solutions of casein and its hydrolysate with an equimolar mixture of amino acids was compared by measuring the X-ray-induced chemiluminescence. It was shown that free amino acids constituting the protein produce long-lived radicals. It was demonstrated that some amino acids (Leu, Ile, Val, Ser, Trp, Met, Pro, Arg, Gly, Phe) emit light of visible spectrum over a long period of time after irradiation, which indicates generation of long-lived radicals of these amino acids. The half-life times of these radicals are several hours. Dissolution of irradiated dry amino acids capable of luminescing over a long time causes formation of hydrogen peroxide in the aqueous medium.     

Two Groups of Amino Acids Interact with GABA-A Receptors Coupled to t-[35S]Butylbicyclophosphorothionate Binding Sites: Possible Involvement with Seizures Associated with Hereditary Amino Acidemias

Seven L-amino acids (Trp, Arg, Lys, Met, Ile, Val, and Phe) partially (28-81%) reversed the inhibitory action of 1 microM gamma-aminobutyric acid (GABA) on t-[35S]butylbicyclophosphorothionate ([35S]TBPS) binding to rat brain membranes, with EC50 values ranging from 5 to 120 mM. D-Trp, D-Arg, D-Lys, D-Met, D-Val, and D-Phe were approximately equipotent with their L-isomers. Tyramine, phenethylamine, and tryptamine, the decarboxylation products of the aromatic amino acids (Tyr, Phe, and Trp, respectively), reversed the inhibitory action of 1 microM GABA on [35S]TBPS binding more potently than the parent amino acids (EC50 values = 1.5-3.0 mM). Human hereditary amino acidemias involving Arg, Lys, Ile, Val, and Phe are associated with seizures, and these amino acids and/or their metabolites may block GABA-A receptors. Five other L-amino acids (ornithine, His, Glu, Pro, and Ala) as well as Gly and beta-Ala inhibited [35S]TBPS binding with IC50 values ranging from 0.1 to 37 mM, and these inhibitions were reversed by the GABA-A receptor blocker R 5135 in all cases. The inhibitory effects of L-ornithine, L-Ala, L-Glu, and L-Pro were stereospecific, because the corresponding D-isomers were considerably less inhibitory. L-His, D-His, and L-Glu gave incomplete (plateau) inhibitions. Human hereditary amino acidemias involving L-ornithine, His, Pro, Gly, and beta-Ala are also associated with seizures, and we speculate that these GABA-mimetic amino acids may desensitize GABA-A receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Amino acid- and purine ribonucleoside-induced germination of Bacillus anthracis DeltaSterne endospores: gerS mediates responses to aromatic ring structures

Specific combinations of amino acids or purine ribonucleosides and amino acids are required for efficient germination of endospores of Bacillus anthracis DeltaSterne, a plasmidless strain, at ligand concentrations in the low-micromolar range. The amino acid L-alanine was the only independent germinant in B. anthracis and then only at concentrations of >10 mM. Inosine and L-alanine both play major roles as cogerminants with several other amino acids acting as efficient cogerminants (His, Pro, Trp, and Tyr combining with L-alanine and Ala, Cys, His, Met, Phe, Pro, Ser, Trp, Tyr, and Val combining with inosine). An ortholog to the B. subtilis tricistronic germination receptor operon gerA was located on the B. anthracis chromosome and named gerS. Disruption of gerS completely eliminated the ability of B. anthracis endospores to respond to amino-acid and inosine-dependent germination responses. The gerS mutation also produced a significant microlag in the aromatic-amino-acid-enhanced-alanine germination pathways. The gerS disruption appeared to specifically affect use of aromatic chemicals as cogerminants with alanine and inosine. We conclude that efficient germination of B. anthracis endospores requires multipartite signals and that gerS-encoded proteins act as an aromatic-responsive germination receptor.     

Growth requirements of hyperthermophilic sulfur-dependent heterotrophic archaea isolated from a shallow submarine geothermal system with reference to their essential amino acids.

Three hyperthermophilic sulfur-dependent heterotrophs were isolated from a shallow submarine hydrothermal system at an inlet of Kodakara-jima island, Kagoshima, Japan. The isolates grew at 60 to 97 degrees C, with the optimum temperatures at 85 to 90 degrees C. Sensitivity to rifampin and the existence of ether lipids indicated that the isolates are hyperthermophilic archaea. Partial sequencing of the genes coding for 16S rRNA showed that the three isolates are closely related to the genus Thermococcus. They grew on proteinaceous mixtures, such as yeast extract, Casamino Acids, and purified proteins (e.g., casein and gelatin), but not on carbohydrates or organic acids as sole carbon and energy sources. Nine amino acids were essential for growth of isolate KS-1 (Thr, Leu, Ile, Val, Met, Phe, His, Tyr, and Arg). Isolate KS-2 required Lys in addition to the nine amino acids, and KS-8 required Lys instead of Tyr. In comparative studies, it was shown that Thermococcus celer DSM 2476 required 10 amino acids (Thr, Leu, Ile, Val, Met, Phe, Tyr, Trp, Lys, and Arg) while Pyrococcus furiosus DSM 3638 required only Ile and Val. The hyperthermophilic fermentative eubacterium Thermotoga neapolitana DSM 4359 did not require any amino acids for growth.     

Roles of the P1, P2, and P3 residues in determining inhibitory specificity of kallistatin toward human tissue kallikrein

Kallistatin is a serpin with a unique P1 Phe, which confers an excellent inhibitory specificity toward tissue kallikrein. In this study, we investigated the P3-P2-P1 residues (residues 386-388) of human kallistatin in determining inhibitory specificity toward human tissue kallikrein by site-directed mutagenesis and molecular modeling. Human kallistatin mutants with 19 different amino acid substitutions at each P1, P2, or P3 residue were created and purified to compare their kallikrein binding activity. Complex formation assay showed that P1 Arg, P1 Phe (wild type), P1 Lys, P1 Tyr, P1 Met, and P1 Leu display significant binding activity with tissue kallikrein among the P1 variants. Kinetic analysis showed the inhibitory activities of the P1 mutants toward tissue kallikrein in the order of P1 Arg > P1 Phe > P1 Lys >/= P1 Tyr > P1 Leu >/= P1 Met. P1 Phe displays a better selectivity for human tissue kallikrein than P1 Arg, since P1 Arg also inhibits several other serine proteinases. Heparin distinguishes the inhibitory specificity of kallistatin toward kallikrein versus chymotrypsin. For the P2 and P3 variants, the mutants with hydrophobic and bulky amino acids at P2 and basic amino acids at P3 display better binding activity with tissue kallikrein. The inhibitory activities of these mutants toward tissue kallikrein are in the order of P2 Phe (wild type) > P2 Leu > P2 Trp > P2 Met and P3 Arg > P3 Lys (wild type). Molecular modeling of the reactive center loop of kallistatin bound to the reactive crevice of tissue kallikrein indicated that the P2 residue required a long and bulky hydrophobic side chain to reach and fill the hydrophobic S2 cleft generated by Tyr(99) and Trp(219) of tissue kallikrein. Basic amino acids at P3 could stabilize complex formation by forming electrostatic interaction with Asp(98J) and hydrogen bond with Gln(174) of tissue kallikrein. Our results indicate that tissue kallikrein is a specific target proteinase for kallistatin.     

Synergistic Effects of High Hydrostatic Pressure,Mild Heating,and Amino Acids on Germination and Inactivation of Clostridium sporogenes Spores

The synergistic effects of high hydrostatic pressure (HHP), mild heating, and amino acids on the germination of Clostridium sporogenes spores were examined by determining the number of surviving spores that returned to vegetative growth after pasteurization following these treatments. Pressurization at 200 MPa at a temperature higher than 40°C and treatment with some of the 19 l-amino acids at 10 mM or higher synergistically facilitated germination. When one of these factors was omitted, the level of germination was insignificant. Pressures of 100 and 400 MPa were less effective than 200 MPa. The spores were effectively inactivated by between 1.8 and 4.8 logs by pasteurization at 80°C after pressurization at 200 MPa at 45°C for 120 min with one of the amino acids with moderate hydrophobicity, such as Leu, Phe, Cys Met, Ala, Gly, or Ser. However, other amino acids showed poor inactivation effects of less than 0.9 logs. Spores in solutions containing 80 mM of either Leu, Phe, Cys, Met, Ala, Gly, or Ser were successfully inactivated by pasteurization by more than 5.4 logs after pressurization at 200 MPa at 70°C for 15 to 120 min. Ala and Met reduced the spore viability by 2.8 and 1.8 logs, respectively, by pasteurization at a concentration of 1 mM under 200 MPa at 70°C. These results indicate that germination of the spores is facilitated by a combination of high hydrostatic pressure, mild heating, and amino acids.     

Relative reactivity of lysine and other peptide-bound amino acids to oxidation by hypochlorite

Antibacterial and inflammatory responses of neutrophils and macrophages produce hypochlorite as a major oxidant. Numerous side chains of amino acids found in extracellular proteins can be modified by hypochlorite, including His, Arg, Tyr, Lys, Trp, and Met. We studied the relative reactivity of each of these amino acid residues in short N-blocked peptides, where other residues in the peptide were highly resistant to hypochlorite attack. Hypochlorite treatment led to modified peptides in each case, which were detected by changes in retention on reversed-phase HPLC. A distinct single product, consuming two equivalents of hypochlorite per equivalent of peptide, was obtained from the Lys-containing peptides. UV spectroscopy, nuclear magnetic resonance (NMR), and electrospray/mass spectroscopy identified this product as the dichloramine at the epsilon-amino group of the Lys side chain. The dichloramine at Lys did not decompose to form a detectable amount of carbonyl reactive with dinitrophenylhydrazine. The dichloramine at Lys did however quantitatively revert back to Lys during HCl digestion of the tetrapeptide for amino acid analysis, with simultaneous modification of the adjacent Phe residue. The formation of the dichloramine at Lys was not blocked by peptides or acetylated amino acids that contained Tyr, His, or Arg. In contrast, the presence of equimolar Met-containing peptide, or N-Acetyl-Trp, both inhibited the formation of the dichloramine at Lys. Thus, Met and Trp side chains of proteins might be able to protect Lys from chloramine formation under some circumstances, but this interpretation must consider that Met and Trp are typically found in relatively inaccessible hydrophobic sites, whereas lysine is typically exposed on the protein surface. The hierarchy of amino acid reactivities examined here will aid in the prediction of residues in biological samples most likely to be modified by hypochlorite.     

Amino acid analysis by high-performance liquid chromatography of a single stained protein band from a polyacrylamide gel

A single stained band containing approximately 5 micrograms of protein was cut out of a polyacrylamide gel and subjected to hydrolysis together with the gel. The hydrolysate was subsequently analyzed for its amino acid content by high-performance liquid chromatography and postlabeling with o-phthalaldehyde. Bovine serum albumin, ribonuclease B, ovalbumin, pepsin, and chymotrypsinogen A were analyzed by this method, and their amino acid compositions were found to be in good agreement with the reported values. By this method, it is possible to quantitate 16 amino acids: Asx, Thr, Ser, Glx, Pro, Cys, Gly, Ala, Val, Ile, Leu, Tyr, Phe, His, Lys, and Arg. Thioglycolic acid is effective protection against the decomposition of Tyr, Cys, and Met; however, the recovery of Met is inconsistent. This method might be very helpful for the amino acid analysis of proteins of multicomponent systems, especially, those which can be resolved only by polyacrylamide gel electrophoresis.     

甘肃鼢鼠骨骼19种氨基酸含量的测定

用121型氨基酸分析仪对甘肃鼢鼠(Myospalax cansus)躯干、四肢、头骨骨骼中19种氨基酸含量进行测定,并与高原鼢鼠及其他哺乳动物骨骼中氨基酸含量进行差异显著性分析。结果表明,甘肃鼢鼠各部位骨骼中19种氨基酸含量均为甘氨酸最高,谷氨酸次之,胱氨酸最低。同一氨基酸在甘肃鼢鼠不同骨骼部位含量顺序为躯干>四肢(头骨。甘肃鼢鼠骨骼总氨基酸含量低于塞隆骨,与虎骨相近,高于其他哺乳动物。其中羟脯氨酸含量明显高于虎骨、塞隆骨等。     

Selective amino acid restriction targets mitochondria to induce apoptosis of androgen-independent prostate cancer cells

Relative specific amino acid dependency is one of the metabolic abnormalities of cancer cells, and restriction of specific amino acids induces apoptosis of prostate cancer cells. This study shows that restriction of tyrosine and phenylalanine (Tyr/Phe), glutamine (Gln), or methionine (Met), modulates Raf and Akt survival pathways and affects the function of mitochondria in DU145 and PC3, in vitro. These three restrictions inhibit energy production (ATP synthesis) and induce generation of reactive oxygen species (ROS). Restriction of Tyr/Phe or Met in DU145 and Met in PC3 reduces mitochondrial membrane potential (DeltaPsim) and induces caspase-dependent and -independent apoptosis. In DU145, Tyr/Phe or Met restriction reduces activity of Akt, mitochondrial distribution of phosphorylated Raf and apoptosis inducing factor (AIF), and increases mitochondrial distribution of Bak. Mitochondrial Bcl-XL is increased in Tyr/Phe-restricted but decreased in Met-restricted cells. Under Tyr/Phe or Met restriction, reduced mitochondrial Raf does not inactivate the pro-apoptotic function of Bak. Tyr/Phe restriction also inhibits Bcl-2 and Met restriction inhibits Bcl-XL in mitochondria. These comprehensive actions damage the integrity of the mitochondria and induce apoptosis of DU145. In PC3, apoptosis induced by Met restriction was not associated with alterations in intracellular distribution of Raf, Bcl-2 family proteins, or AIF. All of the amino acid restrictions inhibited Akt activity in this cell line. We conclude that specific amino acid restriction differentially interferes with homeostasis/balance between the Raf and Akt survival pathways and with the interaction of Raf and Bcl-2 family proteins in mitochondria to induce apoptosis of DU145 and PC3 cells.     

Specificity of DNA-basic polypeptide interactions. III. Sequential and random copolymers of lysine and aromatic amino acids.

Sequential and random lysine copolymers containing various amounts of different aromatic amino acids were synthesized. The sequential copolypeptides exhibited strong dependence of yield and degree of polymerization on the amino acid sequence of the repeating unit. To elucidate the specific contributions of aromatic side chains to the interaction of these copolymers with DNA, direct-mixed complexes were studied by thermal denaturation and CD. The melting behaviour of peptide-bound DNA was found to be strongly affected by amino acid composition and sequence. The contribution of the different aromatic amino acids to thermal stability decreased in the order: polylysine > [Lys, Tyr]_n > [Lys,Phe]_n > [Lys,(OMe)Tyr]_n. The CD spectrum of DNA was altered by random copolymers, whereas sequential copolymers exhibited no changes. The influence of the random copolymers on the CD spectrum of DNA decreased in the series: polylysine > [Lys,Phe]_n > [Lys,(OMe)Tyr]_n > [Lys,Tyr]_n. The contribution of the different aromatic amino acids to thermal stability is interpreted as stacking tendencies toward denatured and, in the case of Tyr, H-bond formation with native DNA. The differences found for the random and the sequential polypeptides can best be explained by assuming a cooperative action of rather small peptide segments.     

烧伤患者血浆和红细胞游离氨基酸变化及输注氨基酸对其变化的影响

动态测定烧伤患者血浆及红细胞内游离氨基酸的含量 ,探讨输入外源性氨基酸后对血及红细胞内游离氨基酸的影响。以日立 835— 5 0型氨基酸自动分析仪测定烧伤患者血浆及红细胞内游离氨基酸含量。结果发现烧伤患者血浆总游离氨基酸浓度从伤后到 2 1天均显著降低 (P <0 .0 5～ 0 .0 1) ;赖、苯丙和苯丙 酪氨酸比值显著升高 (P <0 .0 5～ 0 .0 1) ;色、组、精、丙、甘、苏、脯和丝氨酸比值显著降低 (P <0 .0 5～ 0 .0 1) ;缬、亮、异亮、酪、胱和支链氨基酸伤后早期降低。烧伤患者红细胞内总游离氨基酸含量不同程度降低 ,其中 1、3、7天降低显著 (P <0 .0 5～ 0 .0 1) ;红细胞内苯丙和苯丙 酪氨酸比值未见显著性升高 ;色、蛋、精、脯氨酸含量很低或基本未测出。输注复合氨基酸注射液后未能显著改善患者血及红细胞内游离氨基酸含量。结果提示烧伤患者红细胞内游离氨基酸含量的变化趋势与血浆游离氨基酸变化趋势基本一致 ;烧伤后红细胞内苯丙氨酸及苯丙 酪氨酸比值有别于血浆变化。本研究条件下补充外源性氨基酸未能显著改变烧伤患者血浆及红细胞内游离氨基酸的含量     

Subcellular distribution of aminoacyl-transfer RNA synthetases in Chinese hamster ovary cell culture

Chinese hamster ovary cells grown in cell culture were broken and fractionated by differential centrifugation. Four principal fractions: nuclear and membrane, microsomal, postribosomal, and supernatant were obtained. The distribution of aminoacyl-tRNA synthetases in these four fractions was determined for all twenty amino acids.It was shown that there is a differential distribution of synthetases. Activities specific for eight amino acids: Ala, Ser, Gly, Cys, His, Arg, Thr and Pro were found mainly in the supernatant fraction. Activities specific for eleven amino acids: Asp, Asn, Glu, Gln, Ile, Leu, Lys, Met, Phe, Tyr and Val were found mainly in the postribosomal fraction. Four activities were found at significant levels in the microsomal fraction: Asp, Phe, Lys and Pro. The nuclear and membrane fraction contained activity for Lys, His, Asp and Thr.Changes in aminoacyl-tRNA synthetase activities in various fractions from preparations made by breaking cells with a membrane-dissociating detergent showed that some of the aminoacyl-tRNA synthetase activities may be membrane bound.     

Differential geometry and protein conformation. V. Medium-range conformational influence of the individual amino acids

A previous differential geometric analysis of the conformational properties of the various amino acids has been extended to study their influence on folding over a larger backbone interval. In addition, statistical effects associated with variation in the number of the individual amino acids in the database have been treated in greater detail, using a simulation method. It is found that the amino acids can be divided into three groups on the basis of their conformational influence over four-C^α units in the interval i ? 6 ? j ? i + 6. Group Ia is composed of seven amino acids (His, Leu, Ala, Met, Lys, Gln, Ile) that encourage the formation of A_R-helical structure. Group Ib (Glu, Phe, Trp, Val, Asp) is composed of amino acids with some helix-forming tendency but that also show positive extended-strand formation tendency. They therefore act as a bridge between group Ia and group II (Cys, Gly, Asn, Pro, Arg, Ser, Thr, Tyr) that contains amino acids that encourage the formation of extended structure and bends. The detailed four-C^α conformational properties of each of the amino acids are shown, and the ability of amino acids to exert conformational influence in both directions along the backbone is examined. It is shown that, in general, such influence extends farther in the N-terminal direction than in the C-terminal direction. A framework is briefly sketched for using the present data to investigate actual folding mechanisms.     

Amino acids content and electrophoretic profile of camel milk casein from different camel breeds in Saudi Arabia

This study aimed to evaluate amino acids content and the electrophoretic profile of camel milk casein from different camel breeds. Milk from three different camel breeds (Majaheim, Wadah and Safrah) as well as cow milk were used in this study.Results showed that ash and moisture contents were significantly higher in camel milk casein of all breeds compared to that of cow milk. On the other hand, casein protein of cow milk was significantly higher compared to that of all camel milk breeds. Molecular weights of casein patterns of camel milk breeds were higher compared to that of cow milk.Essential (Phe, Lys and His) and non-essential amino acids content was significantly higher in cow milk casein compared to the casein of all camel milk breeds. However, there was no significant difference for the other essential amino acids between cow casein and the casein of Safrah breed and their quantities in cow and Safrah casein were significantly higher compared to the other two breeds. Non-essential amino acids except Arg and the essential amino acids (Met, Ile, Lue and Phe) were also significantly higher in cow milk α-casein compared to α-casein from all camel breeds. Moreover, essential amino acids (Val, Phe and His) and the non-essential amino acids (Gly and Ser) content was significantly higher in cow milk β-casein compared to the β-casein of all camel milk breeds and the opposite was true for Lys, Thr, Met and Ile. However, Met, Ile, Phe and His were significantly higher for β-casein of Majaheim compared to the other two milk breeds. The non-essential amino acids (Gly, Tyr, Ala and Asp) and the essential amino acids (Thr, Val and Ile) were significantly higher in cow milk κ-casein compared to that for all camel milk breeds. There was no significant difference among all camel milk breeds in their κ-casein content of most essential amino acids.Relative migration of casein bands of camel milk casein was not identical. The relative migration of α_s-, β- and κ-casein of camel casein was slower than those of cow casein. The molecular weights of α_s-, β- and κ-casein of camel caseins were 27.6, 23.8 and 22.4 KDa, respectively. More studies are needed to elucidate the structure of camel milk.