Lewis structure and resonance for arginine ion

I'm working through a problem set in MIT's open courseware 'Principles of Chemical Science' course [here](https://ocw.mit.edu/courses/5-111sc-principles-of-chemical-science-fall-2014/resources/mit5_111f14_lec10prob/). In question 5, it asks:



> 
> The skeletal structures of two amino acids, leucine and arginine, are drawn below. Non-zero formal charges are indicated. Provide the Lewis structure(s), including double bonds and lone pairs, for each of these molecules. If there are equivalent resonance forms (which may include moving the formal charge on N), include them
> 
> 
> 


This arginine structure is given for part (b):


[![arginine ion structure](https://i.stack.imgur.com/uMkPM.png)](https://i.stack.imgur.com/uMkPM.png)


I've been able to produce the resonance structures given in the solution sheet ([here](https://ocw.mit.edu/courses/5-111sc-principles-of-chemical-science-fall-2014/resources/mit5_111f14_lec10soln/)).


[![arginine solutions](https://i.stack.imgur.com/IYbet.png)](https://i.stack.imgur.com/IYbet.png)


But I've also produced another resonance structure which I think is valid but it was not included in the solutions. I've put the formal charge on on the non-terminal N atom. My structure seems to satisfy the octet rule for all atoms and has the same number of bonds and electron pairs as the other solutions. Is there something I'm missing here?


[![my additional](https://i.stack.imgur.com/f0imt.png)](https://i.stack.imgur.com/f0imt.png)


