Dogfish amino acid sequence

The amino acid sequences of corresponding regions from dogfish M4 and Bacillus stearothermophilus lactate dehydrogenases are shown below ... 

The three-dimensional structure of the ternary complex of the dogfish enzyme with NAD and pyruvate is a separate and independent structure determination 136c). The two maps can be interpreted with the same overall fold of polypeptide chain and amino acid sequence. A list of a-car-bon coordinates and dihedral angles for both the apo- and ternary complex structures is given in Table V. 

This tetrameric enzyme (subunit 36000) has been the subject of several crystallographic studies (summarized in [55]), and information on the dogfish isozyme has been obtained at high resolution [78]. The subunit structure [79] is illustrated in Fig. 18. On the basis of crystallographic findings, a numbering system for the amino acid chain was introduced [80], and has been widely used [55,79,81]. What were already known as Ser-163, Arg-171 and His-195 would simply become Ser-161, Arg-169 and His-193 in the consecutively numbered complete sequence [82]. However, in other parts of the chain (notably around residue 33, residue 187, and the regions 135-147 and 236-252) there were more extensive differences. For simplicity,... 

The complete sequence of dogfish M4 LDH, consisting of 329 amino acid residues, has been determined (125,126) and is shown in Fig. 3. Numbering in Fig. 3 was introduced by Rossmann et al. (127) and will be used throughout this article even though a few discontinuities occur,... 

For the IgM of the dogfish shark, Marchalonis and Edelman reported molecular weights of 980,000 (19 S) and 198,000 (7 S) (15). After reduction, alkylation, and exposure to 8 M urea, H chains (mol. wt. 72,000) and L chains (26,000) were liberated in equimolar amounts. Very similar results were obtained with the immunoglobulin of the leopard shark (33). In addition, it has been shown that the N-terminal sequence of six amino acids is the same for the H chains of the 7 S and 19 S forms (34). The N-terminal residue is glutamic acid, rather than cyclized glutamic acid this was the first of many demonstrations of an unblocked amino-terminus in an H chain. (It is now known that some of the H chains of the shark have a blocked N-terminal group.)... 

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