**2. Glutathione S-transferase genes in ticks**

Ticks are blood feeding external parasites of mammals, birds, and reptiles throughout the world. Tick infestations of animals and especially farm ones like cattle and camels, economi‐ cally impact food industry by reducing weight gain and milk production, and by transmit‐ ting pathogens that cause babesiosis (*Babesia bovis* and *Babesia bigemina*) and anaplasmosis (*Anaplasma marginale*). The most important and widely distributed ticks include American dog tick (*Dermacentor variabilis*) is the most commonly identified species responsible for transmitting *Rickettsia rickettsii*, which causes Rocky Mountain spotted fever in humans, *R. microplus* and *R. annulatus* which infest cattle and distributed in Asia, Latin America, and Africa, *Hyalomma dromedarii* which infest camels (Asia and Africa), and the blacklegged tick (*Ixodes scapularis*), commonly known as "deer tick" and can transmit the organisms responsi‐ ble for anaplasmosis, babesiosis, and Lyme disease and is widely distributed in the north‐ eastern and upper midwestern United States.

Acaricide application constitutes a major component of integrated tick control strategies [11]. However, use of acaricides has had limited efficacy in reducing tick infestations and is often accompanied by serious drawbacks, including the selection of acaricide-resistant ticks, environmental contamination, and contamination of milk and meat products with drug resi‐ dues.

GST enzymes are one of the important supergene families that are involved in protecting the organism from oxidative stress and xenobiotics including the acaricides. Different studies have been carried out to explore the role of the different GST families in detoxification in ticks. The methods applied in these studies used biochemical approaches, direct cloning us‐ ing consensus sequences or using the available information from whole genome sequence information. Niranjan Reddy et al. [12] studied the GST superfamily organization in *Ixodes scapularis* using the whole genome sequence information (IscaW1.1, December' 2008) by ap‐ plying different phylogenetic and bioinformatic tools. They identified all the three broad GST classes, the canonical, mitochondrial, and microsomal forms. A total of 35 GST genes belong to five different canonical GST classes, namely Delta (7 genes), Epsilon (5), Mu (14), Omega (3), and Zeta (3 genes) GST classes, and two mitochondrial Kappa class GST genes, and a single microsomal GST gene were found. The analysis of these sequences identified members of the Delta- and Epsilon-classes which are thought to be specific to the Insecta. Surprisingly, Ixodes has lost two of the functionally important gene families, Theta-and Sig‐ ma-GSTs.

Ticks are blood sucking ectoparasites that infest a wide array of species. They are vectors of diseases in humans and other animals. The southern cattle tick, *Rhipicephalus microplus*, transmits the cattle fever pathogen (*Babesia spp*.) and is one of the most important cattle pests. Chemical pesticides continue to be the primary means of control for ectoparasites on livestock. Intensive use of these materials has led to the development of resistance in Rhipi‐ cephalus ticks to all currently used organophosphates [8], synthetic pyrethroids and ami‐ dines [9]. Despite previous studies that suggested increased detoxification [10] and target site insensitivity may contribute to the increased tolerance to acaricides, the mechanisms

An Integrated View of the Molecular Recognition and Toxinology - From Analytical Procedures to Biomedical

In the past years, significant advancement has been made to determine the potential role of GSTs in toxicology. Besides the well established role of GSTs in detoxification of xenobiotic compounds, it has been observed that GSTs have other intracellular substrates including the metabolites released from cellular molecules. In ticks, GSTs have attracted attention because of their involvement in the defense towards insecticides mainly organophosphates, organo‐ chlorines and cyclodienes. This chapter will give highlight on some of the cloned GST genes in ticks and will discuss and review the folding and unfolding states of a GST mu class from

Ticks are blood feeding external parasites of mammals, birds, and reptiles throughout the world. Tick infestations of animals and especially farm ones like cattle and camels, economi‐ cally impact food industry by reducing weight gain and milk production, and by transmit‐ ting pathogens that cause babesiosis (*Babesia bovis* and *Babesia bigemina*) and anaplasmosis (*Anaplasma marginale*). The most important and widely distributed ticks include American dog tick (*Dermacentor variabilis*) is the most commonly identified species responsible for transmitting *Rickettsia rickettsii*, which causes Rocky Mountain spotted fever in humans, *R. microplus* and *R. annulatus* which infest cattle and distributed in Asia, Latin America, and Africa, *Hyalomma dromedarii* which infest camels (Asia and Africa), and the blacklegged tick (*Ixodes scapularis*), commonly known as "deer tick" and can transmit the organisms responsi‐ ble for anaplasmosis, babesiosis, and Lyme disease and is widely distributed in the north‐

Acaricide application constitutes a major component of integrated tick control strategies [11]. However, use of acaricides has had limited efficacy in reducing tick infestations and is often accompanied by serious drawbacks, including the selection of acaricide-resistant ticks, environmental contamination, and contamination of milk and meat products with drug resi‐

GST enzymes are one of the important supergene families that are involved in protecting the organism from oxidative stress and xenobiotics including the acaricides. Different studies have been carried out to explore the role of the different GST families in detoxification in ticks. The methods applied in these studies used biochemical approaches, direct cloning us‐

conferring resistance on ticks are poorly understood.

the cattle tick *Rhipicephalus annulatus* distributed in Egypt.

**2. Glutathione S-transferase genes in ticks**

eastern and upper midwestern United States.

dues.

Applications

268

GSTs had been reported to play a major role in the organophosphate resistance pathway of the *Musca domestica* (Corrnell-HR strain) [13]. On the contrary, Li et al. [14] reported that GSTs play only a minor role against organophosphate toxicity in *R. microplus*. Several GST coding frames had been cloned from *R. microplus* as done by [15] (accession number AAL99403), and [16] described that the activity of this protein is enhanced by organophos‐ phate and coumaphos.

Some GST genes were cloned from different tick species and are of the mu class. The conser‐ vation score is represented in figure 1, and three state secondary structure is in figure 2. However, several attempts were carried out to explore the distribution of the different GST classes in ticks. The most widely distributed and economically important; the cattle tick *R. microplus* was used to initiate a study of the genome using an expressed sequence tag (EST) approach [17]. They reported the construction of a gene index named BmiGI from 20417 ESTs derived from a normalized cDNA library. The BmiGI was used to identify genes which might be involved in the acaricide resistance including GSTs.

Gurrero et al. [17] reported 15 possible GST coding genes identified from the BmiGI. One of these sequences was reported to be similar to the human GST class Omega 1, and the other clone was similar to mouse GST of Zeta 1 class. The total 15 clones are listed in table 1.
