Tryptophanyl circular dichroism in a special hemoglobin

Wollmer, Axel; Buse, Gerhard

doi:10.1016/0014-5793(71)80377-0

Cited by 10 publications

(2 citation statements)

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“…Similar types of CD spectra have been recorded for chymotrypsinogen A (Strickland et al, 1969), lysozyme (Teichberg et al, 1970), cytochrome c (Myer, 1968), and the hemoglobin III component from Chironomus thummi thummi (Wollmer and Buse, 1971). In all these cases there is a broad negative 'La 0-0 band at about 297 nm and a sharper positive 'Lb 0-0 band at about 290 nm and they are attributed to rigid tryptophans, probably hydrogen bonded in a nonpolar environment.…”

Section: Discussionsupporting

confidence: 64%

Circular dichroism studies of myoglobin and leghemoglobin

Nicola¹,

Minasian²,

Appleby³

et al. 1975

Biochemistry

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The circular dichroism spectra of leghemoglobin a from the root nodules of soybean have been compared with those for sperm whale myoglobin in the fat- and near-ultraviolet and the Soret and visible regions of the spectrum. Circular dichroism spectra in the far-ultraviolet show that the leghemoglobins all have a high alpha-helix content (soybean leghemoglobin a, 55%) regardless of the nature of bound ligands and oxidation or spin state of the heme iron. The known sequence homologies with mammalian hemoglobins may therefore be reflected in conformational homologies as suggested by the x-ray studies of Vainshtein et al. ((1975) Nature (London) 254, 163-164) on lupin leghemoglobin. Removal of the heme moiety decreases helicity by only 9% for leghemoglobins, compared with 23% for myoglobin. This, the much smaller heme contribution to the near-ultraviolet circular dichroism than in myoglobin, and the greater accessibility of the heme moiety to aqueous solvent (Nicola et al. (1974), Proc. Aust. Biochem. Soc. 7, 21) suggest that the association between heme and protein is much weaker in leghemoglobins than in myoglobin. The aromatic Soret and visible circular dichroism spectra for all derivatives of leghemoglobin are opposite in sense to those for myoglobin, showing that the patterns of protein side chain contacts with the heme are different in the two classes of heme proteins. There is strong evidence that one of the two tryptophans whose identity and structural role in myoglobin is known, is present also in plant leghemoglobins, hydrogen-bonded and in a similar nonpolar environment whether heme is present or not. The above findings help to explain the remarkably high oxygen affinity and some other ligand-binding properties of leghemoglobins which differ from those of myoglobin.

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Section: Discussionsupporting

confidence: 64%

Circular dichroism studies of myoglobin and leghemoglobin

Nicola¹,

Minasian²,

Appleby³

et al. 1975

Biochemistry

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“…5), the most striking feature being a narrow positive band a t 292nm resolved to some extent also in the absorption spectrum. I n a preceding communication [16] this peak was shown to originate in tryptophan, and, most probably, in a specific tryptophan residue (A12) with restricted conformational mobility. tion point of which is identical with the pK value of the protolysis reaction.…”

Section: In [5])mentioning

confidence: 99%

A Myoglobin‐Type Haemoglobin of Chironomus thummi thummi

Wollmer¹,

Buse²,

Sick³

et al. 1972

European Journal of Biochemistry

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A monomeric haemoglobin of the insect Chironomus thummi thummi is described which does not exhibit a Bohr effect. The thermodynamic parameters AG, A H , and A S are given for the oxygen association. There is a difference of 4 cal per degree in the AS values for the acid and alkaline pH. The absence of a Bohr effect a t physiological temperatures is explained by the fact that there is a point of intersection a t 25 "C in the -AG versus T plot for acid and alkaline pH. This point is designated the "isoaffinity temperature". I n the case of other monomeric Chironomus haemoglobins a Bohr effect is observable because their isoafhity temperatures are remote from the physiological temperature range (haemoglobin I11 = 184 "C, haemoglobin IV = 377 "C).No conformation isomers can be distinguished by circular dichroism and absorption measurements at 25 "C; isosbestic triangles are not encountered in this case.Electron spin resonance spectroscopy, however, carried out a t 77 K, reveals the existence of at least two conformation isomers distinguished by specific high-and low-spin signals. I n case of high-spin H,O-Hb(II1) the acid conformation is characterized by a rhombic distortion of the intramolecular electric field and strong interaction of the d-electrons of the iron with the two nuclei of the bound imidazole. Transition to the alkaline conformation is followed by a change to axial symmetry and weak interaction of the d-electrons with the imidazole.I n the case of OH-Hb(II1) two sets of low-spin signals describe two conformations with different rhombic symmetry.By comparing the positions of histidine residues in haemoglobins I, I11 and IV possible Bohr proton-binding sites are discussed.Myoglobins and haemoglobins are considered to be typical vertebrate respiratory proteins. However, proteins comparable in spectrum and molecular weight are also found in avertebrates. Within the large group of insects only the genus Chironomus contains a n oxygen-carrying haemoprotein of low molecular weight not appearing in erythrocytes but in the haemolymph. This genus belongs to the order of diptera, having giant chromosomes in their salivary glands. Tichy [I] has been able to correlate certain haemoglobins with bands of these giant chromosomes, i.e. to localize certain haemoglobin genes.Sequence analysis [2] and X-ray crystallography [3] have shown that the structural organisation of these haemoproteins is homologous to that of vertebrate haemoglobins. Quite a number of different haemoglobins are found in the haemolymph of Chironomus thummi thummi. Therefore it is possible to realize different conditions of one specific function with these proteins. Chironomus haemoglobins are, therefore, adequate subjects to study the problem of how structure and function are related t o genetic information. The isoelectric points of these haemoglobins range from pH 5.5 to 6.5, only one of them being characterized by a markedly alkaline isoelectric point (pH 8.6) [7], namely haemoglobin I. The physicochemical properties of this haemoglobin are almo...

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