Hemocyanins and Invertebrate Evolution

Holde, Kensal E. van; Miller, Karen I.; Decker, Heinz

doi:10.1074/jbc.r100010200

Cited by 301 publications

(203 citation statements)

References 33 publications

Supporting

Mentioning

187

Contrasting

Unclassified

Order By: Relevance

“…Between them one molecule oxygen is reversibly bound in side-on (l-g 2 :g 2 ) coordination (4,7,9,10). In most hemocyanins, oxygen binding is highly cooperative and tightly controlled by allosteric effectors (1,2,11,12).…”

Section: Introductionmentioning

confidence: 99%

The refined structure of functional unit h of keyhole limpet hemocyanin (KLH1‐h) reveals disulfide bridges

et al. 2011

Self Cite

View full text Add to dashboard Cite

Hemocyanins are multimeric oxygen‐transport proteins in the hemolymph of many arthropods and mollusks. The overall molecular architecture of arthropod and molluscan hemocyanin is very different, although they possess a similar binuclear type 3 copper center to bind oxygen in a side‐on conformation. Gastropod hemocyanin is a 35 nm cylindrical didecamer (2 × 10‐mer) based on a 400 kDa subunit. The latter is subdivided into eight paralogous “functional units” (FU‐a to FU‐h), each with an active site. FU‐a to FU‐f contribute to the cylinder wall, whereas FU‐g and FU‐h form the internal collar complex. Atomic structures of FU‐e and FU‐g, and a 9 Å cryoEM structure of the 8 MDa didecamer are available. Recently, the structure of keyhole limpet hemocyanin FU‐h (KLH1‐h) was presented as a Cα‐trace at 4 Å resolution. Unlike the other seven FU types, FU‐h contains an additional C‐terminal domain with a cupredoxin‐like fold. Because of the resolution limit of 4 Å, in some loops, the course of the protein backbone could not be established with high certainty yet. Here, we present a refined atomic structure of FU‐h (KLH1‐h) obtained from low‐resolution refinement, which unambiguously establishes the course of the polypeptide backbone and reveals the disulfide bridges as well as the orientation of bulky amino acids. © 2011 IUBMB IUBMB Life, 63(3): 183–187, 2011

show abstract

Section: Introductionmentioning

confidence: 99%

The refined structure of functional unit h of keyhole limpet hemocyanin (KLH1‐h) reveals disulfide bridges

et al. 2011

Self Cite

View full text Add to dashboard Cite

show abstract

“…One particular class of material we have investigated are hemocyanins, which are large multisubunit proteins functioning as respiratory proteins in the hemolymph of arthropods and mollusks (19)(20)(21). One of the hemocyanins best investigated is the 4 ϫ 6-meric hemocyanin (Hc) from the tarantula Eurypelma californicum.…”

mentioning

confidence: 99%

Two-photon excitation microscopy of tryptophan-containing proteins

Lippitz

Erker²,

Decker³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

We have examined the feasibility of observing single protein molecules by means of their intrinsic tryptophan emission after two-photon excitation. A respiratory protein from spiders, the 24-meric hemocyanin, containing 148 tryptophans, was studied in its native state under almost in vivo conditions. In this specific case, the intensity of the tryptophan emission signals the oxygen load, allowing one to investigate molecular cooperativity. As a system with even higher tryptophan content, we also investigated latex spheres covered with the protein avidin, resulting in 340 tryptophans per sphere. The ratio of the fluorescence quantum efficiency to the bleaching efficiency was found to vary between 2 and 180 after two-photon excitation for tryptophan free in buffer solution, in hemocyanin, and in avidin-coated spheres. In the case of hemocyanin, this ratio leads to about four photons detected before photobleaching. Although this number is quite small, the diffusion of individual protein molecules could be detected by fluorescence correlation spectroscopy. In avidin-coated spheres, the tryptophans exhibit a higher photostability, so that even imaging of single spheres becomes possible. As an unexpected result of the measurements, it was discovered that the population of the oxygenated state of hemocyanin can be changed by means of a one-photon process with the same laser source that monitors this population in a two-photon process.

show abstract

“…For details, see the text. T∆S°was calculated based on T∆S°) ∆H°+ RT ln K. 40). This Janus-faced efficient uptake and delivery of oxygen by the respiratory pigment is modulated by various effectors.…”

Section: Discussionmentioning

confidence: 99%

Allosteric Models for Multimeric Proteins: Oxygen-Linked Effector Binding in Hemocyanin

et al. 2005

Self Cite

View full text Add to dashboard Cite

In many crustaceans, changing concentrations of several low molecular weight compounds modulates hemocyanin oxygen binding, resulting in lower or higher oxygen affinities of the pigment. The nonphysiological effector caffeine and the physiological modulator urate, the latter accumulating in the hemolymph of the lobster Homarus vulgaris during hypoxia, increase hemocyanin oxygen affinity and decrease cooperativity of oxygen binding. To derive a model that describes the mechanism of allosteric interaction between hemocyanin and oxygen in the presence of urate or caffeine, studies of oxygen, urate, and caffeine binding to hemocyanin were performed. Exposure of lobster hemocyanin to various pH values between 7.25 and 8.15 resulted in a decrease of p50. In this pH interval, p50 decreases from 95 to 11 Torr without effectors and from 49 to 6 Torr and from 34 to 5 Torr in the presence of 1 mM urate or caffeine, respectively. Thus, the allosteric effects induced by protons and urate or caffeine are coupled. In contrast, isothermal titration calorimetry did not reveal any differences in binding enthalpy (ΔH°) for urate or caffeine under either normoxic or hypoxic conditions at different pH values. Despite these apparently conflicting results, they can be explained by the nested MWC model if two different types of modulator binding sites are assumed, an allosteric and a nonallosteric type of site. Simulations of in vivo conditions with this model indicate that the naturally occurring modulator urate is physiologically relevant in H. vulgaris only during hypoxic conditions, i.e., either during environmental oxygen limitation or extensive exercise.

show abstract

Hemocyanins and Invertebrate Evolution

Cited by 301 publications

References 33 publications

The refined structure of functional unit h of keyhole limpet hemocyanin (KLH1‐h) reveals disulfide bridges

The refined structure of functional unit h of keyhole limpet hemocyanin (KLH1‐h) reveals disulfide bridges

Two-photon excitation microscopy of tryptophan-containing proteins

Allosteric Models for Multimeric Proteins: Oxygen-Linked Effector Binding in Hemocyanin

Contact Info

Product

Resources

About